Co-reporter:Shishui Liu, Wu Xiao, Shaofeng Zhang, Xuemei Wu, Shiqi Huang, Lin Ma, Wei Chen, Dongxing Zhen, and Gaohong He
ACS Sustainable Chemistry & Engineering October 2, 2017 Volume 5(Issue 10) pp:8738-8738
Publication Date(Web):August 23, 2017
DOI:10.1021/acssuschemeng.7b01520
In the present work, a special competitive adsorbent, ethanol, is proposed for in situ release product inhibition of a hydrophobic product system from a hydrophobic carbon catalyst support. Product inhibition is serious in electrochemical hydrogen pump hydrogenation reactors (EHPRs) due to slow molecular diffusion of the products through the microporous flow channels (1–10 μm). The hydrogenation rate of maleic acid decreases rapidly with reaction time, only 37.4% retention after 10 h reaction. By introducing ethanol in the aqueous solution, both reaction rate and conversion after 10 h reach 1.46 folds of those without ethanol. Evidenced by competitive adsorption, the adsorption capacity of the product amber acid is decreased by 98% on carbon particles compared with that without ethanol. Ethanol takes most of the place of amber acid due to much better affinity with carbon support, which releases more amber acid molecules into the bulk solution and relieves product inhibition. Kinetics parameters are fitted with modified Langmuir–Hinshelwood kinetics by considering the influence of ethanol competitive adsorption on maleic acid hydrogenation performance.Keywords: Adsorption effect; Biomass hydrogenation; Catalyst layer; Electrochemical hydrogen pump hydrogenation reactor; Product inhibition;
Co-reporter:Ning Zhang, Yuechun Song, Jun Huo, Yan Li, Zhao Liu, Junjiang Bao, Shaomin Chen, Xuehua Ruan, and Gaohong He
The Journal of Physical Chemistry C June 29, 2017 Volume 121(Issue 25) pp:13840-13840
Publication Date(Web):June 12, 2017
DOI:10.1021/acs.jpcc.7b01074
The structure of the hydrogen bond network inside of the proton conductive channel is of significant importance to proton transfer confined in a nanochannel. In order to investigate the independent effects of fluorination and confinement dimension on the hydrogen bond network, a one-dimensional carbon nanotube decorated with fluorine was built to mimic the environment of the proton conductive channel in the perfluorosulfonic membrane ( Phys. Chem. Chem. Phys. 2016, 18 (35), 24198−24209). It was found that a fluorinated nanochannel helps to form a spiral-like sequential hydrogen bond network with few branched hydrogen bonds in the central region, which is believed to promote unidirectional proton transfer along the channel axis without random movement. To explore the mechanism of the formation of the spiral-like hydrogen bond structure, molecular dynamics simulation was conducted to analyze the hydrogen bonding properties of water and a hydrated proton confined in the fluorinated CNT with chirality of (10,10). The hydrogen bond criteria were initially evaluated for the water–water and hydronium–water hydrogen bonds. It was found that the confined hydrated protons help maintain the connectivity of the hydrogen bond network along the axis of the fluorinated nanochannel at different temperatures. The hydronium ion prefers to form hydrogen bonds with two neighboring water molecules, resulting in a continuous hydrogen bond network. The non-hydrogen-bonded hydrogen atom of the hydronium ion has strong attraction with the fluorinated channel surface, stabilizing the hydrogen bond structure and making space in the central region of the nanochannel. The connectivity of the hydrogen bond network and the interaction between hydronium and the channel surface produce the spiral-like structure of the hydrogen bond network along the axis of the fluorinated nanochannel with few branched hydrogen bonds.
Co-reporter:Xue Gong, Xiaoming Yan, Tiantian Li, Xuemei Wu, Wanting Chen, Shiqi Huang, Yao Wu, Dongxing Zhen, Gaohong He
Journal of Membrane Science 2017 Volume 523() pp:216-224
Publication Date(Web):1 February 2017
DOI:10.1016/j.memsci.2016.09.050
•A novel approach is proposed to design AEMs with flexible ether-containing side chain.•Enhanced mobility of side chains and ion interactions promote micro-phase separation.•Conductivity (72 mS cm−1) and swelling (7.3%) are well balanced even at 60 °C.•Good alkaline stability (60 °C, 1 M KOH for 168 h) is obtained.A novel approach is proposed to design anion exchange membranes (AEMs) containing pendent imidazolium side chains with flexible ether-containing spacer by the Williamson etherification between chloromethylated polysulfone and as-synthesized hydroxyl-bearing imidazolium. The introduction of long flexible ether-containing spacer chains enhances the mobility of terminated imidazolium groups and ion interactions. It facilitates the formation of a good hydrophilic/hydrophobic micro-phase separation structure, which is confirmed by the scattering peak of SAXS. As a result, the membranes exhibit high conductivity and excellent anti-swelling ability. The membrane with IEC of 1.55 mmol g−1 shows considerable hydroxide conductivity (72 mS cm−1, 60 °C), low swelling ratio (7.3%, 60 °C), and great tensile strength in hydrated state (43.4 MPa, 20 °C). The existence of long spacer chain also improved the alkaline stability. After immersion in 60 °C, 1 M KOH solution for 168 h, hydroxide conductivity and tensile strength of the membrane remain constant. The ether-containing side chains fabricated in this work provides a universal promising method to balance hydroxide conductivity and dimensional and alkaline stability.
Co-reporter:Xiaoming Yan, Caimian Zhang, Yan Dai, Wenji Zheng, Xuehua Ruan, Gaohong He
Journal of Membrane Science 2017 Volume 544(Volume 544) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.memsci.2017.09.025
•A novel imidazolium-based amphoteric membrane was prepared.•The membrane shows low vanadium permeability and high conductivity.•The VFB cell employing this membrane achieved high performance.A novel amphoteric membrane was prepared using imidazolium-functionalized polysulfone (ImPSf) as the base polymer and sulfonated poly (ether ether ketone) (SPEEK) as the acid polymer for vanadium flow battery applications. The introduction of the ImPSf effectively resists the migration of vanadium ions owing to the Donnan repelling effect of the imidazolium cations on the vanadium ions and the low swelling ratio of the amphoteric membranes due to the ionic cross-linked interactions between the imidazolium and sulfonic groups. The amphoteric membrane with an ImPSf mass ratio of 17% shows a vanadium permeability of 1.5 × 10−8 cm2 s−1 that is much lower than that of Nafion212 (21 × 10−8 cm2 s−1). Having a high IEC of 2.04 mmol g−1, it also exhibits a low area resistance of 0.48 Ω cm−2 that is comparable to that of Nafion212 membrane (0.41 Ω cm−2). As a result, the VFB cell with the amphoteric membrane exhibits high performances even at high current densities, i.e. at a current density of 200 mA cm−2, and the amphoteric membrane achieves a coulombic efficiency of 97.5% and an energy efficiency of 77.3%, both of which are higher than those of Nafion212 (92.4% and 73.4%). These results indicate that the ImPSf/SPEEK amphoteric membrane is promising for VFB applications.
Co-reporter:Junjiang Bao, Yan Lin, Gaohong He
International Journal of Refrigeration 2017 Volume 82(Volume 82) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.ijrefrig.2017.05.025
•A transcritical power and ejector refrigeration cycle (TPERC) is proposed.•Seven working fluids are used.•R1234ze has the largest thermal efficiency and exergy efficiency.•There is a generation pressure at which the work output reaches its maximum.The combined power and cooling cycles driven by waste heat and renewable energy can provide different kinds of energy forms and achieve a higher thermodynamic efficiency. However, only a few researchers have focused on the improvement of temperature matching between the heat source and working fluid. This paper proposes a transcritical power and ejector refrigeration cycle (TPERC) to improve temperature matching between the heat source and working fluid. Based on the modelling of the TPERC system, a comparison of working fluids and the effects of system parameters on the cooling capacity, work output, thermal efficiency and exergy efficiency are discussed. The results show that of the seven working fluids selected, R1234ze has the largest thermal efficiency and exergy efficiency, principally due to having the highest critical temperature. At the identical turbine back pressure, condensing temperature and evaporation temperature, the turbine inlet temperature and its corresponding generation pressure have little impact on thermal efficiency.
Co-reporter:Junjiang Bao, Yan Lin, Ruixiang Zhang, Ning Zhang, Gaohong He
Applied Thermal Engineering 2017 Volume 126(Volume 126) pp:
Publication Date(Web):5 November 2017
DOI:10.1016/j.applthermaleng.2017.07.144
•Effects of stage number of condensing process are discussed.•Three traditional systems and four proposed systems are considered.•Net power output, electricity production cost and annual net income.•The two-stage condensation combined cycle is recommended.Due to the large temperature change of LNG regasification process (from about −160 °C to ambient temperature), the irreversible loss of the LNG regasification process is large, which affects the efficiency of power generation systems for LNG cold energy recovery. Our previous study proposed a two-stage condensation Rankine cycle, which can effectively improve the utilization efficiency of LNG. On this basis, this paper continues to discuss the effect of stage number of condensing process on the performance and economy of the power generation systems by LNG cold energy. Seven systems are considered in this paper, including three traditional power generation systems (direct expansion, organic rankine cycle and combined cycle) and four proposed systems (the two-stage and three-stage condensation Rankine cycles, as well as the two-stage and three-stage combined cycles). These seven systems are simulated by Aspen Hysys software, and with net power output, electricity production cost (EPC) and annual net income as the objective functions respectively, the key system parameters (the condensation temperature and the inlet pressure of LNG turbine, etc.) are optimized under the three different objective functions. Results showed that when the net power output is the objective function, the net power output of the three-stage combined cycle is the largest. If EPC is chosen as the objective function, the cost of the combined cycle is always lower than that of the Rankine cycle system with the same condensation stage number, but net power output of the Rankine cycle is higher than that of the combined cycle. When annual net income is the objective function, the three-stage combined cycle has the largest annual net income. But if considering the difficult degree of control system, the two-stage combined cycle is recommended.
Co-reporter:Xiaoming Yan, Runlian Deng, Yu Pan, Xiaowei Xu, Issam El Hamouti, Xuehua Ruan, Xuemei Wu, Ce Hao, Gaohong He
Journal of Membrane Science 2017 Volume 533(Volume 533) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.memsci.2017.03.032
•The interactions between polar nitrile groups and cation groups were proved.•PEN based HEMs show good alkaline stability.•PEN based HEMs have high hydroxide conductivity and low swelling ratio.Hydroxide exchange membrane fuel cells (HEMFCs) are attracting growing interest owing to their advantages such as low cost and high power density. However, their applications are hindered due to the poor stability of the membrane. Here, we proposed a novel strategy to improve the alkaline stability of hydroxide exchange membranes (HEMs) using the interactions between strongly polar nitrile groups and side-chain functional cations. A poly(ether nitrile) (PEN) was synthesized by the polycondensation of bisphenol A and 2,6-difluorobenzonitrile, and then imidazolium and morpholinium functional groups were integrated by the typical chloromethylation-functionalization method. The existence of the interactions between nitrile groups and cation groups i.e. imidazolium and morpholinium, was proved by the density functional theory calculations. The interactions have two positive effects that contribute to the improvement of the alkaline stability of the PEN based membranes. On the one hand, they increase the LUMO energies of the functional groups; and on the other hand they reduce the free volume around hydrated cationic groups. As a result, PEN based membranes showed much better alkaline stabilities compared to the membrane based on commercial polysulfone that has a similar chemical structure. In addition, given similar swelling ratios, PEN based membranes exhibited higher hydroxide conductivities than simple polysulfone based ones.
Co-reporter:Bingyan Han;Rongchao Xiang;Xufen Hou;Mingbo Yu;Tingting Peng;Ying Li
Analytical Methods (2009-Present) 2017 vol. 9(Issue 17) pp:2590-2595
Publication Date(Web):2017/05/04
DOI:10.1039/C7AY00625J
Rich-thymine (T) single- or double-strand DNAs have been identified as efficient templates favoring the formation of fluorescent copper nanoparticles (Cu NPs). In this work, we confirmed single base T could be a template to synthesize water-soluble copper nanoclusters (Cu NCs@T) for the first time. Our work provided basic evidence of the benefit of using T-rich DNA strands for the synthesis of fluorescent Cu NPs. Transmission electron microscopy demonstrated that Cu NCs@T had a diameter of 2.8 ± 0.5 nm, which is much smaller than Cu NPs templated by single- or double-strand DNAs. X-ray photoelectron spectroscopy confirmed the valence state of the Cu in Cu NCs@T most likely lies between 0 and +1. The as-prepared Cu NCs@T exhibited yellow photoluminescence and the maximum excitation and emission peaks were at 354 nm and 561 nm, respectively. In addition, we also showed that the as-prepared Cu NCs@T can be developed into a practical sensor for “turn-on” luminescence with the emission red-shifted detection of Mn2+ in aqueous solution with a high selectivity. The limit of detection for Mn2+ was determined to be 10 μM and the linear response with the Mn2+ concentrations range from 100 μM to 250 μM.
Co-reporter:Wanting Chen;Mengmeng Hu;Haochen Wang;Xuemei Wu;Xue Gong;Xiaoming Yan;Dongxing Zhen
Journal of Materials Chemistry A 2017 vol. 5(Issue 29) pp:15038-15047
Publication Date(Web):2017/07/25
DOI:10.1039/C7TA01218G
A novel alkaline group, hexamethylenetetramine (HMTA) with four tertiary amine groups and β-hydrogen-absent structure, has been employed as mono-quaternization reagent to prepare HMTA mono-quaternized polysulfone anion exchange membranes (PSF-QuOH AEMs). Analyzed by molecular dynamics simulations, mono-quaternized HMTA shows a superior aggregating ability by strong electrostatic interaction with hydroxide to suppress water swelling even at high IECs. In particular, the PSF-QuOH membrane with a high IEC of 2.23 mmol g−1 exhibits a low swelling ratio of 21% even at 60 °C. The resulting high concentration of cationic groups and the interactions between multiple hydrogen atoms in HMTA and hydroxide/water are helpful to induce the formation of the continuous and efficient hydrogen-bond networks, promoting ionic transport. High hydroxide conductivity of 35 mS cm−1 is achieved at 20 °C. Excellent swelling resistance also benefits the mechanical and chemical stabilities of the PSF-QuOH membranes. A considerable mechanical strength of 17.7 MPa is observed in the fully hydrated membrane. The hydroxide conductivity is stable at around 86% of the initial value after 1 M KOH immersion at 60 °C for 168 h.
Co-reporter:Xiaopeng Zhang;Zhuofeng Li;Jijun Zhao
Korean Journal of Chemical Engineering 2017 Volume 34( Issue 7) pp:2065-2071
Publication Date(Web):26 May 2017
DOI:10.1007/s11814-017-0092-3
Various physico-chemical techniques and theoretical chemistry computations are used to obtain a deep insight into the mechanism of Ce improving SO2 resistance of the catalyst Mn0.4Cex/Al2O3 (x stands for the molar ratio of Ce : Al). Theoretical computation with density functional theory (DFT) shows that Ce modification enhances the adsorption energy of SO2 adsorbed on Ce surrounding, resulting in the preferential adsorption of SO2 on Ce surrounding. It protects the surface Mn from SO2 poisoning, leading to a better SO2 resistance. FT-IR and TG results are in good accordance with DFT results. FT-IR results suggest that absorption peaks related to SO42− cannot be detected in Mn0.4Ce0.12/Al2O3. Moreover, TG results show that weight loss peaks due to sulfated MnOx decomposition disappears after Ce addition. Therefore, Ce modification inhibits sulfates formation on active components lead to a better resistance to SO2 of Mn0.4Ce0.12/Al2O3.
Co-reporter:Ning Zhang, Zhao Liu, Xuehua Ruan, Xiaoming Yan, Yuechun Song, Zhuanglin Shen, Xuemei Wu, Gaohong He
Chemical Engineering Science 2017 Volume 158(Volume 158) pp:
Publication Date(Web):2 February 2017
DOI:10.1016/j.ces.2016.10.015
•We investigated Hyfion@ perfluorosulfonic acid membranes with various water uptake.•We described confinement effect of channel in membrane on hydrated proton structure.•The confined complexes of H9O4+, H7O3+ and H5O2+ take the dominant role.•Weakening confinement effect leads to the formation of the complex H9O4+.In polyelectrolyte membranes, hydrated protons and proton conductive channels have cooperative effect on proton conductivity, the mechanism of which is believed to involve the structure of hydrated proton being deformed to adapt the confining channel. To investigate the dependence of the structural and dynamical properties of hydrated protons in Hyfion® perfluorosulfonic acid membranes with various water uptake values on the channel size, a series of molecular dynamics simulations based on an all-atom force field were conducted. The water uptake dependence of the hydrated proton diffusivity determined from our simulations was consistent with the experimental results in literature, which verified the simulation systems. A probability distribution of the hydrated proton complex is proposed to characterize the confinement effect of the proton conductive channel on the hydrated proton structure in the membranes with different morphologies. By means of local structural properties and pair-potential energies, a reasonable hydrogen bond criterion was employed to characterize the structures of the hydrated proton complexes. It was found that the nanochannels confined the structure of the hydrated proton complex and that confined complexes of H9O4+, H7O3+ and H5O2+ were dominant. Weakening the confinement by increasing the channel size was beneficial for the formation of the H9O4+ complex, the probability distribution of which gradually became plateau. Thus, H9O4+ can be considered the stable structure of the confined hydrated proton complex in polymer electrolyte membranes. This work is helpful in understanding the relationship between the structure of the confined hydrated proton and the proton conductive channel. It also provides potential guidance for improving the membrane performance in fuel cell.Download high-res image (132KB)Download full-size image
Co-reporter:Xinhong Qi, Wenji Zheng, Gaohong He, Tianfang Tian, Naixu Du, Le Wang
Chemical Engineering Journal 2017 Volume 309(Volume 309) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.cej.2016.10.060
•NiCo2O4 HMs are facilely synthesized by RF-COOH microspheres hard templates method.•Shell numbers and thickness of NiCo2O4 HMs are tuned by varying synthesis parameters.•The thin shell NiCo2O4 HMs show superior supercapacitor performance to thick shell.We report a new resin formaldehyde (RF-COOH) microspheres hard templates based method to synthesize NiCo2O4 hollow microspheres with thin/thick single/double/triple-shell. Single-shell NiCo2O4 hollow microspheres are obtained with deionized water as solvent. Furthermore, ethylene glycol can decrease the aquo groups (H2O) number within the coordination sphere of Ni2+/Co2+, which leads to a decrease of hydrated metal ions size and more penetrated metal ions into RF microspheres that is essential to the formation of more shells. Thus, double and triple-shell NiCo2O4 hollow microspheres are harvested when ethylene glycol is solvent and the heating ramp rate are 2 and 5 °C/min, respectively. Larger heating ramp rate (2–5 °C/min) increases the temperature gradient of the infused RF microspheres, which favors the separation between adjacent NiCo2O4 layers and RF cores, and thus resulting in the formation of more shells. What’s more, shells become thick and more compact when the precursor concentration is increased from 0.05 to 0.1 M due to more infused Ni2+/Co2+. The electrochemical performance for supercapacitors of NiCo2O4 hollow microspheres with thin multi-shells is superior to those with thick single-shell. The better performances are attributed to multi-shells with more electroactive sites and hollow structures as “ion-buffering reservoir”, while thin shell is beneficial to the diffusion of electrolyte/ions.NiCo2O4 hollow microspheres (HMs) with thin/thick single/double/triple-shell are synthesized based on the resin formaldehyde (RF-COOH) microspheres hard templates method. Shell numbers are facilely tuned by modifying solvent and heating ramp rate. Shell thickness can also be controlled through varying the precursor concentration.Download high-res image (187KB)Download full-size image
Co-reporter:Xiaopeng Zhang, Yuezong Cui, Jinxin Wang, Bojian Tan, Chengfeng Li, Hang Zhang, Gaohong He
Chemical Engineering Journal 2017 Volume 326(Volume 326) pp:
Publication Date(Web):15 October 2017
DOI:10.1016/j.cej.2017.06.014
•Mn0.1/Co0.3-Ce-ZrO2 had excellent simultaneous removal activity of NO and Hg0.•The interaction of flue gas components lowered simultaneous removal activity.•The interaction between Hg0 and SCR atmosphere was investigated.•Mechanisms of simultaneous removal of NO and Hg0 were also studied.Hg0 removal with SCR system can result in co-benefits of the apparatus, but the simultaneous removal efficiencies of Hg0 and NO are not good enough and the mechanism of interaction between Hg0 and SCR atmosphere has not been well known. In our previous work, Co0.3-Ce0.35-Zr0.35O2 has been proved to have an excellent Hg0 oxidation efficiency. Therefore, in the present work, Co0.3-Ce0.35-Zr0.35O2 was used as a support to load SCR active component Mn and to obtain Mn0.1/Co0.3-Ce0.35-Zr0.35O2 catalyst. Mn0.1/Co0.3-Ce0.35-Zr0.35O2 showed excellent simultaneous efficiencies of Hg0 oxidation (83.6%) and NO conversion (89.4%) at 180 °C under a high GHSV 180,000 h−1. Furthermore, the interaction between Hg0 and SCR atmosphere lowered the simultaneous efficiencies when compared to the separated ones. The decrease of Hg0 oxidation efficiency in SCR + Hg0 atmosphere was mainly attributed to the competitive adsorption between NH3 and Hg0. Although NO and O2 were beneficial for Hg0 oxidation, it could not offset the inhibitive effect of NH3. Meanwhile, HgO accumulated on the catalyst surface resulted in occupation of active sites, which was responsible for the decrease of NO conversion in SCR + Hg0 atmosphere. The individual gas components (H2O and SO2) showed negative effects on the simultaneous efficiencies of Hg0 oxidation and NO conversion.Download high-res image (296KB)Download full-size image
Co-reporter:Xiaopeng Zhang, Jinxin Wang, Bojian Tan, Zhuofeng Li, Yuezong Cui, Gaohong He
Catalysis Communications 2017 Volume 98(Volume 98) pp:
Publication Date(Web):10 July 2017
DOI:10.1016/j.catcom.2017.04.024
•Ce-Co catalyst with uniform mesoporous channels was prepared via template method.•Hg0 oxidation activity of Ce-Co maintained above 95% in the range 150–350 °C.•The good catalytic activity was due to high surface area and more active-sites.Ce-Co catalyst was prepared by template method (denoted as Ce-Co-T) and co-precipitation method (denoted as Ce-Co-C) for element mercury oxidation. Structural results showed that Ce-Co-T had a much larger BET surface area (220.01 m2/g) and uniform mesoporous channels along with uniform particle size which could lead to more surface active sites. XPS showed that Ce-Co-T had more surface active oxygen species resulting in a better redox property. Compared with Ce-Co-C, Ce-Co-T had a much better Hg0 oxidation efficiency which maintained above 95% under a high GHSV (180, 000 h− 1) in the range 150–350 °C.Download high-res image (107KB)Download full-size image
Co-reporter:Wenji Zheng, Yanan Dong, Xiaoming Yan, Rui Ding, Gaohong He
Solid State Communications 2017 Volume 262(Volume 262) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.ssc.2017.06.009
•A hybrid PSS/TiO2 nanocrystalline film based UV detector is proposed.•The UV detector exhibits high responsivity, large on/off ratio and low dark current.•The mechanism relies on the energy level match of PSS and TiO2.A hybrid polystyrene sulfate (PSS) modified TiO2 nanocrystalline (NC) composite film based ultrovilet (UV) photodetector (PD) was proposed in this study. TiO2 NC film with uniform size distribution was deposited on FTO glass by doctor blading P25 TiO2 nanoparticles. Through layer-by-layer self-assembly, PSS/TiO2 composite film was prepared and it exhibits a high responsivity of 602 AW−1, a large photo-to-dark current ratio of 193200% and a low dark current of 7 nA at only 0.1 V bias. The obtained high responsivity is almost 1–2 orders of magnitude higher than that of mostly reported TiO2 NC film based UV PDs. The reason is attributed to the injection of electrons from PSS into conduction band of TiO2 and the separation improvement of photogenerated electrons and holes by the rutile/anatase junction in the TiO2 NC film. Considering the high responsive performances and facile low-cost fabrication, the proposed PSS/TiO2 composite film based UV PD shows a bright prospect in large-area UV detection application.
Co-reporter:Wenjuan Zhang, Xuehua Ruan, Yongliang Ma, Xiaobin Jiang, Wenji Zheng, Yuanfa Liu, Gaohong He
Separation and Purification Technology 2017 Volume 179(Volume 179) pp:
Publication Date(Web):31 May 2017
DOI:10.1016/j.seppur.2017.01.022
•Particles accumulation on permeate boundary with baffles is modeled.•Dynamics process of cake formation was quantified and visualized.•The arrangement of turbulence promoter are simulated and optimized by the model.Mitigating membrane fouling by using turbulence promoters (TP) is an important issue in the microfiltration field. Considering the particles accumulation on the walls of permeable membrane tubes (one kind of fouling mechanism) with TP, we proposed a three-dimensional numerical model for random decision that decides particle movement on the membrane boundary. We investigated and predicted the permeate flux, fouling layer thickness and optimal TP arrangement modes with different operational parameters with this model. The dynamics process of cake deposition was precisely quantified and visualized. And then the simulated results ignored of pore blockage for the permeation flux were deviated less than 10% compared with the experimental data in literatures. After TP condition being optimized, the mass transfer resistance sharply reduced. Average thickness of the cake layer decreased from 0.318 mm to 0.026 mm, and the permeate flux increased more than 60%.
Co-reporter:Xuehua Ruan, Hanli Wang, Yan Dai, Xiaoming Yan, Ning Zhang, Xiaobin Jiang, Gaohong He
Separation and Purification Technology 2017 Volume 188(Volume 188) pp:
Publication Date(Web):29 November 2017
DOI:10.1016/j.seppur.2017.07.070
•Polyimide membrane plant for TFE recovery is industrialized for the first time.•Adaptive membrane area control is succeeded to deal with drastic feed fluctuation.•Polyimide membrane plant is excellent with TFE recovery ratio up to 87.6%.•Membrane plant is economically feasible with the payback time less than 4 months.This is a continuation of the development of polyimide membrane for tetrafluoroethylene (TFE) recovery [Sep.Purif.Technol.124(2014)89–98]. A industrial membrane plant has been designed and constructed after cryogenic acetone absorption to enhance TFE recovery for the first time. Specific to the 10-kt/a TFE synthesis plants, the nominal process capacity is set as 20 Nm3/h. The vacuum mode (−0.08 MPaG) is executed for the permeate side to increase the feed/permeate pressure ratio and enhance separation performance under low feed pressure. In response to the drastic fluctuation in feed flow rate and composition, owing to the unsteady cracking reaction, the adaptive control of membrane area is customized technically for the operation strategy. In detail, one or two modules can be shut down by the automatic response while the stream into membrane plant is lower in flow rate or higher in TFE content, and vice versa. In comparison to the ordinary mode under inflexible operation, whose TFE recovery ratio is about 84.5%, the adaptive control strategy behaved better with the recovery ratio up to 87.6%. According to the three-month running result, the membrane recovery plant with adaptive membrane area control can efficiently decrease TFE loss from 130 to 17 t/a, and the annual gross profit was about 1.264 million US dollar, with the payback period less than 4 months. It is undoubted that the polyimide membrane plant is practicable and cost-efficient for TFE recovery in the synthesis.
Co-reporter:Wenji Zheng, Rui Ding, Xiaoming Yan, Gaohong He
Materials Letters 2017 Volume 201(Volume 201) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.matlet.2017.04.133
•ZnO with tunable morphology and band gap is achieved by PEG assisted microemulsion strategy.•A high level of defects are demonstrated to exist in ZnO nanorods.•The band gap energies of ZnO decrease with PEG molecular weight increasing.We demonstrate the fabrication ZnO nanostructures with tunable morphology and band gap by polyethylene glycol (PEG) assisted microemulsion strategy. Rectangular and spindle-like ZnO nanoparticles were obtained for PEG 200, 400 and 1000, while ZnO nanorods were achieved by PEG 10000. The formation mechanism was discussed correspondingly. XRD and PL spectra reveal that the defects in ZnO products are enhanced with PEG molecular weight increasing from 200 to 10000, resulting in the band gap energies decreasing from 3.12 eV to 2.95 eV, as demonstrated in the UV–Vis absorption spectra. The present research work can provide a new way to tune the optical property of ZnO.
Co-reporter:Xuehua Ruan, Xinfang Zhang, Xuhang Liao, Xiaobin Jiang, Yan Dai, Xiaoming Yan, Gaohong He
Journal of Membrane Science 2017 Volume 541(Volume 541) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.memsci.2017.06.068
•Mechanical stability and uniformity of 2-D continuous ZIF-8 membranes are enhanced.•ZIF-8 nucleation and growth are improved by Zn(II)-doped polydopamine coatings.•Aggregated Zn(II) clusters are acting as the starting sites for ZIF-8 nucleation.•An indented and hinged boundary between ZIF-8 and polydopamine layers is achieved.•The 2-D continuous ZIF-8 membranes behave excellent with αH2/CO2 = 9.9 (pure gas).Zeolitic imidazolate framework-8 (ZIF-8) with regular pore size (~ 0.34 nm) is widely attempted for gas separation membranes based on size sieving. However, the prospect is subjected to fabricating the continuous ZIF-8 membranes with high mechanical stability and uniformity. In response, an adhesive layer of Zn(II)-doped polydopamine (Zn-PDA) is pre-coated on the stainless steel nets in this work to improve ZIF-8 nucleation and growth. Zn-PDA layer shows high tolerance to ultrasonic agitation and heated methanol (system for ZIF-8 synthesis), little dissolution within 24 h, which supplies a high stable surface for ZIF-8 growth. Furthermore, the Zn(II) doped in PDA layer is opportunely serving as the even-distributed ZIF-8 nucleation starting sites, verified with the EDX and FE-SEM images for the aggregated Zn(II) clusters and the nascent ZIF-8 crystals. Therefore, an indented and hinged boundary is constructed between ZIF-8 and substrate to enhance the mechanical stability. The FE-SEM images after ultrasonic agitation show that the continuous ZIF-8 membranes prepared on Zn-PDA layers can tolerate the deformation to a certain extent. Finally, the prepared ZIF-8 membranes behave excellently with αH2/CO2 = 9.9, αH2/CO = 17.2, αH2/CH4 = 26.0, and permeation rate JH2 = 3980 GPU. This work supplied a useful approach to enhance mechanical stability and uniformity of defect-free ZIF-8 membranes.
Co-reporter:Wenji Zheng, Tengfei Bian, Xiangcun Li, Meihui Chen, Xiaoming Yan, Yan Dai, Gaohong He
Journal of Alloys and Compounds 2017 Volume 712(Volume 712) pp:
Publication Date(Web):25 July 2017
DOI:10.1016/j.jallcom.2017.04.129
•Self-powered UV detector based on TiO2/Au(Ag/Pt)/TiO2 sandwich structure is proposed.•The UV detector is driven on by two opposite schottky junctions.•The UV detector presents high responsivity and fast response speed.In this study, we demonstrate a relatively independent UV photodetector which is composed of one layer of Au/Ag/Pt metal nanoparticles sandwiched between two layers of n-type TiO2 semiconductor nanorods. Different from most reported Schottky junction based UV photodetectors, it can be driven only by two opposite Schottky junction in the sandwich structure, but no need for any external power supply except UV light when it works. Moreover, it displays high responsivity and fast response speed at the same time, giving a bright prospect for self-powered UV photodetectors.UV photodetector based on the sandwich structure of semiconductor/metal/semiconductor is driven only by two opposite Schottky junctions without any other power resource supply.Download high-res image (444KB)Download full-size image
Co-reporter:Lei Su, Daishuang Zhang, Sangshan Peng, Xuemei Wu, ... Gaohong He
International Journal of Hydrogen Energy 2017 Volume 42, Issue 34(Volume 42, Issue 34) pp:
Publication Date(Web):24 August 2017
DOI:10.1016/j.ijhydene.2017.07.049
•Orientated GO/Nafion ultra-thin layer (440 nm) coated composite membrane is prepared.•Balance of vanadium crossover and H+ conduction by GO orientation in ultra-thin layer.•GO/Nafion exhibits lower capacity decay rate (0.23%) than Nafion 212 over 200 cycles.Graphene oxide (GO)/Nafion composite membranes, with orientated GO nanosheets in parallel to the surface of the ultra-thin coating layer (400–440 nm), are prepared by spin coating method and evidenced by electron microscopy analysis. Orientation of GO maximizes the vanadium ions barrier effect of GO. The GO/Nafion membrane (M-2) achieves lower vanadium ion permeability (8.2 × 10−8 cm2 min−1, only 2.64% of the pristine Nafion membrane), and higher coulombic efficiency and energy efficiency (92.9–98.8% and 81.5–88.4%, respectively) comparing with the pristine Nafion membrane (73.3–90.5% and 68.9–79.1%, respectively) at current densities of 20–100 mA cm−2. With the design of orientated GO nanosheets and ultra-thin GO/Nafion coating layer, good balance between vanadium crossover suppression and protons conduction retention is achieved. M-2 exhibits excellent battery performances over 200 charge-discharge cycles. The capacity decay rate is about 0.23% per cycle, much lower than those assembled with Nafion 212 (0.40% per cycle) and the recast Nafion membrane (0.44% per cycle). Spin coating with water suspensor leads to uniform dispersion of GO and good binding between GO/Nafion coating layer and substrate Nafion membrane. Therefore, the composite membrane could be reinforced by GO and keep integration even with 200 cycles operation.
Co-reporter:Xiaopeng Zhang, Zhuofeng Li, Jinxin Wang, Bojian Tan, Yuezong Cui, Gaohong He
Fuel 2017 Volume 203(Volume 203) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.fuel.2017.04.065
•SO2 had different effects on Hg0 adsorption and oxidation process.•Active sites was deactivated by SO2 resulting in a bad Hg0 adsorption efficiency.•The forming sulphates acted as new active sites in Hg0 oxidation process.•Catalysts still had good Hg0 oxidation efficiency in the presence of SO2.The removal of Hg0 from flue gas has been one of the primary challenges in the control of mercury emission. The presence of even small amounts of SO2 has a significant influence on the Hg0 removal process, and the mechanism of this process has not been thoroughly explained to date. To understand the mechanism for SO2 influence, the influence of SO2 on the Hg0 adsorption and Hg0 oxidation components of the Hg0 removal process were investigated separately based on Ce0.1-Zr-MnO2. SO2 was shown to have serious negative effects on the Hg0 adsorption process due to the reaction between SO2 and Mn-based active sites, as determined by TGA and XPS results. In contrast, for the Hg0 oxidation process Mn-SO42− formed through the reaction between SO2 and Mn-based active sites, and Mn-SO42− had a certain contribution to Hg0 oxidation. Moreover, XPS results indicated that SO2 reacts with O2 to form SO3 which adsorbed on the catalyst surface and act as new active sites, promoting Hg0 oxidation via: Hg + SO3 + 1/2O2 → HgSO4. This phenomenon caused the catalyst to retain Hg0 oxidation activity in the presence of SO2 for a relatively long time.Download high-res image (84KB)Download full-size image
Co-reporter:Sangshan Peng;Xiaoming Yan;Xuemei Wu;Daishuang Zhang;Yongliang Luo;Lei Su
RSC Advances (2011-Present) 2017 vol. 7(Issue 4) pp:1852-1862
Publication Date(Web):2017/01/04
DOI:10.1039/C6RA24801B
A series of thin skinned asymmetric polybenzimidazole (PBI) membranes with readily tunable morphologies are fabricated by leaching out the porogen dibutyl phthalate (DBP), for vanadium flow batteries (VFBs). The ultrathin defect-free skin layer fully guarantees high ion selectivity of the membrane. Meanwhile, the area resistance (AR) of the asymmetric PBI membrane is dramatically reduced compared to that of the dense one because of interconnected macro-pores in the sublayer. The membrane morphologies and properties are readily adjusted by varying the porogen content (0–300 wt%), thus managing well the trade-off between AR and ion selectivity. The membrane prepared by adding 200 wt% porogen has a high porosity of 74.9 vol% and an appropriately dense skin thickness of 4.9 μm, and yields the best balance between AR and ion selectivity, assembled with which the flow battery achieves excellent cell performances (coulombic efficiency, CE: 99.0%; energy efficiency, EE: 82.3%) as well as a moderate capacity decay rate (CDR, 0.4% per cycle) at 80 mA cm−2 over cycling. The thin skinned asymmetric PBI membranes prepared here surpass the commercial Nafion 211 membrane (CE: 84.6%; EE: 68.1%; CDR: 1.3% per cycle) in terms of cell performances and cost, becoming a promising candidate for VFBs.
Co-reporter:Bingyan Han;Mingbo Yu;Tingting Pen;Ying Li;Xixi Hu;Rongchao Xiang;Xufen Hou
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 13) pp:5267-5270
Publication Date(Web):2017/06/26
DOI:10.1039/C7NJ00858A
Herein, we introduced a kind of physical method using acetone to directly extract fluorescent carbon quantum dots (CQDs) from ordinary carbon black in one step. The as-extracted CQDs exhibited an excitation-dependent emission behavior and a high quantum yield of up to 19.01%. Moreover, we find that the polarity of the solvent will affect the size of CQDs for the first time.
Co-reporter:Bingyan Han;Xufen Hou;Rongchao Xiang
Analytical Methods (2009-Present) 2017 vol. 9(Issue 27) pp:4028-4032
Publication Date(Web):2017/07/13
DOI:10.1039/C7AY01164D
Bimetal nanoclusters (BNCs) have attracted great attention due to their cooperative electronic, optical, and catalytic properties. In this study, the highly luminescent Cu/Ag BNCs were prepared based on the weakly luminescent glutathione (GSH)-capped Cu NCs for the first time. After the introduction of a certain amount of Ag+, a 9-fold enhancement of the luminescence intensity was obtained from GSH-protected Cu/Ag BNCs. The luminescence emission peak was blue shifted from 620 nm (red emission) to 604 nm (orange-yellow emission). The Cu/Ag BNCs exhibited an average size of around 1.4 ± 0.2 nm, as observed from a thorough analysis of transmission electron microscopy data. The as-prepared Cu/Ag BNCs exhibited excellent anti-interference performance against various metal ions. In addition to the intrinsic optical properties, the Cu/Ag BNCs were employed as a temperature sensor by virtue of the luminescence intensity of Cu/Ag BNCs responding sensitively to temperature fluctuating in the range of 4–55 °C.
Co-reporter:Shiqi Huang, Xuemei Wu, Wei Chen, Tao Wang, Yao Wu and Gaohong He
Green Chemistry 2016 vol. 18(Issue 8) pp:2353-2362
Publication Date(Web):27 Oct 2015
DOI:10.1039/C5GC01719J
A bilateral electrochemical hydrogen pump reactor is proposed for the first time. In one electrochemical hydrogen pump (EHP) configuration, in situ adsorbed hydrogen atoms for phenol hydrogenation at the cathode are donated by the dehydrogenation of 2-propanol instead of a conventional H2 or H2O anode feedstock. For the anodic 2-propanol dehydrogenation EHP reactor, by increasing Pt–Ru/C catalyst loading and applying a pulse current operation, the applied potential can be controlled below 0.2 V, which is much lower than the thermodynamic dissociation potential of water (1.23 V). For the cathodic cyclohexanone hydrogenation EHP reactor, the hydrogenation rate reaches 73.9 mmol h−1 g−1Pd, nearly three times of that in aqueous-phase selective hydrogenation reactors. Pd/C and Pt/C catalysts have high catalytic selectivity to cyclohexanone (95.5%) and cyclohexanol (95.4%), respectively. In the bilateral EHP reactor, 2-propanol dehydrogenation and phenol hydrogenation are completed simultaneously, exhibiting a comparable hydrogenation rate, selectivity and conversion to that in the individual EHP reactors. The feasibility of the bilateral EHP reactor provides a novel idea to efficiently integrate multiple reactors into one configuration, which greatly simplifies hydrogen production, storage and transportation, as well as reactor equipment.
Co-reporter:Xiangcun Li, Le Wang, Jianhang Shi, Naixu Du, and Gaohong He
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 27) pp:17276-17283
Publication Date(Web):June 21, 2016
DOI:10.1021/acsami.6b04654
Nickel–cobalt oxides/hydroxides have been considered as promising electrode materials for a high-performance supercapacitor. However, their energy density and cycle stability are still very poor at high current density. Moreover, there are few reports on the fabrication of mixed transition-metal oxides with multishelled hollow structures. Here, we demonstrate a new and flexible strategy for the preparation of hollow Ni–Co–O microspheres with optimized Ni/Co ratios, controlled shell porosity, shell numbers, and shell thickness. Owing to its high effective electrode area and electron transfer number (n3/2 A), mesoporous shells, and fast electron/ion transfer, the triple-shelled Ni–Co1.5–O electrode exhibits an ultrahigh capacitance (1884 F/g at 3A/g) and rate capability (77.7%, 3–30A/g). Moreover, the assembled sandwiched Ni–Co1.5–O//RGO@Fe3O4 asymmetric supercapacitor (ACS) retains 79.4% of its initial capacitance after 10 000 cycles and shows a high energy density of 41.5 W h kg–1 at 505 W kg–1. Importantly, the ACS device delivers a high energy density of 22.8 W h kg–1 even at 7600 W kg–1, which is superior to most of the reported asymmetric capacitors. This study has provided a facile and general approach to fabricate Ni/Co mixed transition-metal oxides for energy storage.
Co-reporter:Xinhong Qi, Xiangcun Li, Bo Chen, Huilan Lu, Le Wang, and Gaohong He
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 3) pp:1922
Publication Date(Web):January 3, 2016
DOI:10.1021/acsami.5b10083
Catalyst-containing nanoreactors have attracted considerable attention for specific applications. Here, we initially report preparation of PtNi@SiO2 hollow microspheres based on confined catalysis. The previous encapsulation of dispersed Pt nanoparticles (NPs) in hollow silica microspheres ensures the formation of Pt@Ni coreshell NPs inside the silica porous shell. Thus, the Pt NPs not only catalyze the reduction of Ni ions but also direct Ni deposition on the Pt cores to obtain Pt@Ni core–shell catalyst. It is worthy to point out that this synthetic approach helps to form a patchlike or thick Ni coating on Pt cores by controlling the penetration time of Ni ions from the bulk solution into the SiO2 microspheres (0.5, 1, 2, or 4 h). Notably, the Pt@Ni core–shell NPs with a patch-like Ni layer on Pt cores (0.5 and 1 h) show a higher H2 generation rate of 1221–1475 H2 mL min–1 g–1cat than the Pt@Ni NPs with a thick Ni layer (2 and 4 h, 920–1183 H2 mL min–1 g–1cat), and much higher than that of pure Pt NPs (224 H2 mL min–1 g–1cat). In addition, the catalyst possesses good stability and recyclability for H2 generation. The Pt@Ni core–shell NPs confined inside silica nanocapsules, with well-defined compositions and morphologies, high H2 generation rate, and recyclability, should be an ideal catalyst for specific applications in liquid phase reaction.Keywords: core−shell; hydrogen generation: catalysis; nanoreactor; Pt@Ni nanoparticles
Co-reporter:Shiqi Huang, Tao Wang, Xuemei Wu, Wu Xiao, Miao Yu, Wei Chen, Fengxiang Zhang, Gaohong He
Journal of Power Sources 2016 Volume 327() pp:178-186
Publication Date(Web):30 September 2016
DOI:10.1016/j.jpowsour.2016.07.025
•Hydrogen separation and butanone hydrogenation are coupled in an EHP with high rate.•Hydrogenation is more stable with SPPESK due to lower swelling and CO2 permeation.•Energy efficiency of the H2/CO2 EHP separator is superior to pure H2 or H2O.This work reports the novel work of coupling H2/CO2 separation with biomass-derived butanone hydrogenation in non-fluorinated sulfonated poly (phthalazinone ether sulfone ketone) (SPPESK) electrochemical hydrogen pump (EHP) reactor. Due to higher resistance to swelling, SPPESK-based EHP reactor exhibits more excellent reaction rate in elevated temperature (60 °C) and higher butanone concentration (2 M) as 270, 260 nmol cm−2 s−1, respectively, higher than 240, 200 nmol cm−2 s−1of Nafion-based EHP reactors. Also, the SPPESK-based EHP reactor remains 90% of initial hydrogenation rate after 4 batches, better than that of Nafion-based EHP reactors, which is only 62%. The energy efficiency of EHP separator reaches 40% under H2/CO2 mixture feed mode, and electricity of about 0.3 kWh is consumed per Nm3 H2 product, being superior to energy consumption compared with alternative processes like PSA and electrolysis of water. In addition, SPPESK-based EHP exhibits better hydrogenation stability due to lower CO2 permeation than Nafion. With increasing CO2 content in H2 feed, hydrogenation rate almost keeps constant at around 210 nmol cm−2 s−1 in SPPESK-based EHP reactor while decreases fast to 50 nmol cm−2 s−1 in Nafion/PTFE-based EHP reactor. These results show integration of gas separation with hydrogenation reactor is feasible in SPPESK-based EHP reactor.
Co-reporter:Xiangcun Li, Le Zhang, Gaohong He
Carbon 2016 Volume 99() pp:514-522
Publication Date(Web):April 2016
DOI:10.1016/j.carbon.2015.12.076
Double-shelled hollow carbon spheres with multiporosity, highly conductive graphite structure and Fe3O4 species was initially prepared (C–C–Fe3O4). The seamless combination between the Fe3O4 species and the porous carbon network leads to a remarkably high capacitivity (1153 F g−1 at 2 A g−1) and good rate capability (514 F g−1 at 100 A g−1) of pseudocapacitive. In addition, the C–C–Fe3O4 assembled asymmetric supercapacitor demonstrates excellent cycling stability (96.7% retention of the initial capacitance after 8000 cycles) and achieves high energy density (17–45 W h kg−1) at powder density of 400–8000 W kg−1. The unique porous carbon structure and seamlessly integration between carbon and Fe3O4 species generate synergistic effect to boost high performance and ideal durability, and high conductivity of the graphitized carbon, the large specific surface area of the hierarchical pore network and the perfectly distributed Fe3O4 redox species in the carbon content also account for its ideal capacitive properties. The multiporous structure could allow efficient diffusion of electrolyte and promote interfacial redox reactions of supercapacitor by facilitating the accessibility of redox active sites, and the highly uniform distribution of Fe3O4 species in the porous carbon makes the best use of conductive carbon network and facilitates good rate capability.
Co-reporter:Xuehua Ruan, Lijuan Wang, Yan Dai, Ning Zhang, Xiaoming Yan, Gaohong He
Separation and Purification Technology 2016 Volume 168() pp:265-274
Publication Date(Web):10 August 2016
DOI:10.1016/j.seppur.2016.05.061
•Ethylbenzene dehydrogenation vent gas was attempted to yield H2 economically.•Membrane and absorption units were integrated to recover H2 efficiently and stably.•Absorption using fresh ethylbenzene was proposed to deeply remove styrene (10 ppm).•Deep removal of styrene inhibits its polymerization and protects separation units.•Multistage cycle absorption was proposed to enrich styrene actively for recovery.Ethylbenzene catalytic dehydrogenation can generate a large amount of hydrogen. Its vent gas is attractive with hydrogen content higher than 75 mol%. Nevertheless, styrene remaining in the vent gas is highly active to polymerize into oligomers, the gradual accumulation of which is harmful to hydrogen separation equipments. In this work, an integral separation process including absorption and membrane units is established to overcome this challenge. Absorption unit running with fresh ethylbenzene as the absorbent is proposed to deeply remove styrene, the residual content of which is reduced to less than 10 ppm. Thereafter, the generation and accumulation of styrene oligomers is restrained strictly to protect hydrogen separation equipments. Furthermore, the custom-designed absorption tower with a multi-stage cycle structure is used to reasonably improve styrene content in the used ethylbenzene at tower bottom, in the interest of reducing styrene recovery expense. For a 100 kt/a styrene plant with the vent gas flow rate up to 3180 N m3/h, a 5-stage tower is designed, which is 0.5 m in diameter, 5.0 m in height, and about 3.0 m in the total packing height of 25-mm metal Intalox saddles. Flow rates of liquids in the tower and the recycle routes are 1.19 m3/h and 1.05 m3/h, respectively. Finally, compressor and membrane for hydrogen recovery are optimized simultaneously with gross profit as the criterion. For compressor, its duty and outlet pressure are 520 kW and 1.85 MPa, respectively. For membrane separation unit, its area and permeation stage cut are 460 m2 and 0.84, respectively. According to the simulation research, this integrated system can behave excellently with an annual recovery of 162 ton styrene, 281 ton aromatic hydrocarbons and 2.1 × 107 N m3 hydrogen, with a gross profit up to 5.1 × 106 US dollars per year.
Co-reporter:Yan Dai, Xuehua Ruan, Zhijun Yan, Kai Yang, Miao Yu, Hao Li, Wei Zhao, Gaohong He
Separation and Purification Technology 2016 Volume 166() pp:171-180
Publication Date(Web):22 June 2016
DOI:10.1016/j.seppur.2016.04.038
•ImGO as a CO2-philic filler was blended in PEBAX to improve CO2 separation ability.•The selectivity of MMM for CO2/N2 increased by 46.0% compared to PEBAX membrane.•ImGO 0.8 exhibited the best CO2 separation performance surpassing the Upper Bound.Mixed matrix membranes (MMMs) were composed of imidazole functionalized graphene oxide (ImGO), a CO2-philic nano-sheet inorganic material, and poly(ether-b-amide) (PEBAX) for CO2 capture. MMM doped with 0.8 wt.% ImGO exhibits the best CO2 separation performance, which shows the CO2/N2 selectivity up to 105.5 combined with CO2 permeability of 76.2 Barrer (1 Barrer = 10−10 cm3(STP) cm cm−2 s−1 cmHg−1), surpassing the Robeson Upper Bound of 2008. The selectivity of MMM for CO2/N2 increases by 46.0% compared to the Pristine PEBAX due to the interaction between CO2 and imidazole groups. With the increase of feed pressure, CO2 permeability increases significantly because of its higher solubility in polymer matrix and plasticization. It is effective to separation CO2 from N2 at lower temperature for MMMs because the apparent activation energy of the N2 permeation process in ImGO/PEBAX MMMs is much higher than that of CO2. Tg of MMMs are increased gradually because the polymer chain mobility is restricted by the presence of ImGO and a rigidified interface generates between polymer and filler. The mechanical properties have been significantly enhanced by the ImGO sheet as expected because of the presence of H-bonding. Having distinct improvement of CO2 separation performance, the ImGO/PEBAX MMMs indicates promising applications in CO2 capture processes.
Co-reporter:Xiaoming Yan, Li Gao, Wenji Zheng, Xuehua Ruan, Caimian Zhang, Xuemei Wu, Gaohong He
International Journal of Hydrogen Energy 2016 Volume 41(Issue 33) pp:14982-14990
Publication Date(Web):7 September 2016
DOI:10.1016/j.ijhydene.2016.06.030
•A spacer-modified imidazolium-functionalized PEEK (PEEK-AeImOH) was synthesized.•The PEEK-AeImOH membrane shows the conductivity as high as 48 mS cm−1.•The PEEK-AeImOH membrane has good stability in 1 M KOH at 60 °C.•High open circuit voltage of 1.02 V and power density of 120 mW cm−2 were achieved.An imidazolium-functionalized poly(ether ether ketone) containing a long spacer chain between imidazolium group and polymer main-chain (PEEK-AeImBr) was synthesized by the reaction of chloromethylated PEEK and self-synthesized 1-Aminoethyl-2,3-dimethylimidazolium bromide. 1H NMR spectra confirmed the successful synthesis of PEEK-AeImBr. The corresponding PEEK-AeImOH HEM was prepared by casting the PEEK-AeImBr solution and subsequent ion-exchange process. Ion exchange capacity (IEC) of PEEK-AeImOH membranes ranges from 1.50 to 2.07 mmol g−1 with the degree of chloromethylation from 58% to 92%. Hydroxide conductivity of PEEK-AeImOH membranes increases with increasing IEC. PEEK-AeImOH membrane with IEC of 2.07 mmol g−1 has the highest conductivity of 48 mS cm−1. The spacer-modified PEEK-AeImOH membrane maintained good alkali stability at 60 °C. The H2/O2 single cell with the PEEK-AeImOH membrane exhibits high open circuit voltage of 1.02 V and peak power density of 120 mW cm−2 at room temperature.
Co-reporter:Sangshan Peng, Xiaoming Yan, Daishuang Zhang, Xuemei Wu, Yongliang Luo and Gaohong He
RSC Advances 2016 vol. 6(Issue 28) pp:23479-23488
Publication Date(Web):24 Feb 2016
DOI:10.1039/C6RA00831C
A H3PO4 preswelling strategy is proposed to prepare H2SO4-doped polybenzimidazole (PBI) membranes for vanadium flow batteries (VFB). Before being immersed in 3.0 M H2SO4, PBI membranes are preswelled by immersion in concentrated H3PO4, which leads to a higher H2SO4 doping level, thereby dramatically reducing the area resistance of the PBI membrane to 0.43 Ω cm2, which is close to that of Nafion 212 (0.35 Ω cm2) and much lower than that of Fumasep®FAP-450 (0.64 Ω cm2). Meanwhile, the substantially high selectivity is maintained. The VFB assembled with the H3PO4 preswelled PBI membrane displays high energy efficiencies (EE: 80.9–89.2%) over a current density range of 20–80 mA cm−2, much higher than those of the non-preswelled PBI membrane (EE: 66.8–84.5%), Nafion 212 (EE: 63.1–75.6%) and Fumasep®FAP-450 (EE: 75.5–82.6%). The stable performance over 50 charge–discharge cycles demonstrates the good physicochemical stability of the preswelled PBI membrane. Considering the above results, the H3PO4 preswelling strategy proposed herein is facile and efficient for fabricating high-performance PBI membranes for VFB.
Co-reporter:Yu Pan, Xiaowei Xu, Ning-Ning Wei, Ce Hao, Xiaodong Zhu and Gaohong He
RSC Advances 2016 vol. 6(Issue 74) pp:69939-69946
Publication Date(Web):07 Jul 2016
DOI:10.1039/C6RA14867K
Polymerization of 1,7-octadiene catalyzed by the (η5-C5Me5)TiCl2(O-2,6-iPr2C6H3)/MAO system exhibited unusual favorable selectivity of repeated insertion. However, the mechanism of selectivity of the insertion mode of non-conjugated dienes has not been reported previously as far as we know. By using the density functional theory (DFT) method, the insertion modes of 1,7-octadiene, especially the selectivity of repeated insertion and intramolecular cyclization, were explored in detail concerning the (η5-C5Me5)TiCl2(O-2,6-iPr2C6H3)/MAO system. At the initiation stage, the 1,2-si-insertion is the optimal pathway among four insertion modes kinetically and thermodynamically. At the chain propagation stage, the competition between repeated insertion and intramolecular cyclization was discussed in detail, concerning the insertion into different growing chains. The computational results indicated that the repeated insertion of 1,7-octadiene showed more kinetically favorable than the intramolecular cyclization in three different situations, with free energy barrier differences between two insertion modes of 3.75 kcal mol−1, 3.88 kcal mol−1 and 7.43 kcal mol−1 respectively. Moreover, the sequential insertion of seven-membered rings exhibited disadvantageous kinetically and thermodynamically, probably due to the steric repulsion effect between two cyclic rings. Those are in good agreement with the experimental data.
Co-reporter:Bo Chen, Xuehua Ruan, Xiaobin Jiang, Wu Xiao, and Gaohong He
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 4) pp:1064-1075
Publication Date(Web):January 12, 2016
DOI:10.1021/acs.iecr.5b04384
A dual-membrane module is able to provide higher separation performance for H2/CO2 gas mixtures compared to conventional single-membrane modules. In this work, the flow patterns of dual-membrane modules are studied, and the results indicate that the co(H2):counter(CO2) flow pattern is the optimal flow pattern for H2 recovery. The co(H2):counter(CO2) flow pattern employs cocurrent (permeate flow parallel to bulk flow) to the H2-selective membrane and counter-current (permeate flow reverse to bulk flow) to the CO2-selective membrane; the flow pattern reduces the permeation flux of CO2 in the H2-selective membrane, resulting in a higher H2 separation factor. The evaluations show that the H2 product purity could be raised by 35% (from 62 mol % to 84 mol %) compared to conventional membrane modules. The results indicate that enhancing the membrane separation performance through flow pattern is a practical and effective method for process engineering.
Co-reporter:Jianwei Li, Xiaoming Yan, Yuyan Zhang, Baolin Zhao and Gaohong He
RSC Advances 2016 vol. 6(Issue 63) pp:58380-58386
Publication Date(Web):08 Jun 2016
DOI:10.1039/C6RA07241K
A new method was proposed to prepare a membrane with regional aggregation of functional groups by incorporating nanocomposites surface-functionalized with a large number of functional groups. Imidazolium surface-functionalized SiO2 (SiO2-Im) nanocomposites were synthesized by the reaction of 1,2-dimethylimidazole, γ-chloropropyl triethoxysilane and SiO2 nanocomposites. The obtained SiO2-Im nanocomposites were incorporated into imidazolium functionalized polysulfone (PSf-Im) to fabricate composite alkaline anion exchange membranes. The uniform dispersion of nanocomposites in the membrane was demonstrated by SEM. With increasing mass ratio of SiO2-Im from 0% to 20%, hydroxide conductivity of composite membrane dramatically increases at first and then decreases. The composite membrane with 12 wt% of SiO2-Im shows the highest conductivity, e.g., the hydroxide conductivity of the composite membrane based on PSf-Im with functionalization degree of 76% reaches 32 mS cm−1 (at 20 °C) that is 68% higher than the membrane's without doping SiO2-Im (19 mS cm−1). In addition, adding SiO2-Im has a slight effect on water uptake and swelling ratio of composite membrane. It indicates that doping surface-functionalized nanocomposites is a simple and effective method to enhance the hydroxide conductivity without increasing swelling.
Co-reporter:Miao Yu, Yan Dai, Kai Yang, Hao Li, Huimin Guo and Gaohong He
RSC Advances 2016 vol. 6(Issue 32) pp:27016-27019
Publication Date(Web):04 Mar 2016
DOI:10.1039/C5RA25029C
Triethanolamine (TEA) was incorporated into a chitosan (CS) matrix to prepare a new blend composite membrane on a polypropylene (PP) microporous substrate. Significant enhancements in mechanical properties, CO2 permeation rate and CO2/N2 selectivity of the thus obtained blend membrane were demonstrated compared with those of the pristine CS membrane.
Co-reporter:Yan Dai, Xuehua Ruan, Feng Bai, Miao Yu, Hao Li, Zongchang Zhao, Gaohong He
Applied Surface Science 2016 Volume 360(Part A) pp:164-173
Publication Date(Web):1 January 2016
DOI:10.1016/j.apsusc.2015.11.014
Highlights
- •
PTFPMS/PEI hollow fiber composite membrane for gas separation was prepared.
- •
Dry membrane and wet membrane dip-coating methods were used and contrasted.
- •
PTFPMS/PEI composite membrane exhibits stable performance after immersed solvent.
Co-reporter:Yuanyuan Sun;Xuemei Wu;Dongxing Zhen;Shikai Zhang;Mengmeng Hu
Journal of Applied Polymer Science 2016 Volume 133( Issue 1) pp:
Publication Date(Web):
DOI:10.1002/app.42867
ABSTRACT
Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) composite membranes are fabricated through electrostatic layer-by-layer (LbL) self-assembly method with chitosan (CS) and phosphotungstic acid (PWA) to enhance the proton conductivity and stability. The results demonstrate that LbL self-assembly has different effects on the SPPESK membrane substrates with different sulfonation degrees (DSs). It elevates proton conductivity of the SPPESK membrane of lower DS and enhances swelling stability of the SPPESK membrane of higher DS. For instance, at 80°C, proton conductivity of the SPPESK0.74/(CS/PWA)1 membrane (lower DS) increases by 16%–96.49 mS cm−1, and swelling ratio of the SPPESK1.01/(CS/PWA)3 membrane (higher DS) decreases from 58 to 29%. Attribute to the electrostatic interaction and ion cross-linking networks, permeability of the SPPESK0.74/(CS/PWA)3 membrane and the SPPESK1.01/(CS/PWA)5 membrane are reduced by 45 and 30%, respectively. The results indicate that the LbL self-assembly has broadened the available DS range for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 132, 42867.
Co-reporter:Zhang Xiaopeng;Cui Yuezong;Li Zhuofeng;Zhou Xuerong ;He Gaohong
Chemical Engineering & Technology 2016 Volume 39( Issue 5) pp:874-882
Publication Date(Web):
DOI:10.1002/ceat.201500574
Abstract
The three catalysts Mn/Ce-ZrO2, MnCo/Ce-ZrO2, and Mn/Co-Ce-ZrO2 were applied to remove NO in simulated flue gas. Their selective catalytic reduction (SCR) activity and potassium resistance were studied. Catalysts with Co as a modifier of the support exhibited the best SCR activity. The catalyst Mn/Co-Ce-ZrO2 had a larger surface area, higher dispersion of active components, larger amount of surface acid, and better redox characteristics than the other two catalysts, leading to a better SCR activity. X-ray photoelectron spectroscopy results proved the higher surface Mn4+ concentration of K0.3Mn/Co-Ce-ZrO2. Pyridine adsorption analysis suggested that there was still a large amount of Lewis acid in Mn/Co-Ce-ZrO2 even after potassium poisoning, demonstrating the higher resistance of this catalyst to potassium. Mn/Co-Ce-ZrO2 with potassium addition had a relatively stable SCR activity in the presence of H2O and SO2.
Co-reporter:Baojun Li;Xiaobin Jiang
Frontiers of Chemical Science and Engineering 2016 Volume 10( Issue 2) pp:255-264
Publication Date(Web):2016 June
DOI:10.1007/s11705-016-1567-1
Hydrogen was recovered and purified from coal gasification-produced syngas using two kinds of hybrid processes: a pressure swing adsorption (PSA)-membrane system (a PSA unit followed by a membrane separation unit) and a membrane-PSA system (a membrane separation unit followed by a PSA unit). The PSA operational parameters were adjusted to control the product purity and the membrane operational parameters were adjusted to control the hydrogen recovery so that both a pure hydrogen product (>99.9%) and a high recovery (>90%) were obtained simultaneously. The hybrid hydrogen purification processes were simulated using HYSYS and the processes were evaluated in terms of hydrogen product purity and hydrogen recovery. For comparison, a PSA process and a membrane separation process were also used individually for hydrogen purification. Neither process alone produced high purity hydrogen with a high recovery. The PSA-membrane hybrid process produced hydrogen that was 99.98% pure with a recovery of 91.71%, whereas the membrane-PSA hybrid process produced hydrogen that was 99.99% pure with a recovery of 91.71%. The PSA-membrane hybrid process achieved higher total H2 recoveries than the membrane-PSA hybrid process under the same H2 recovery of membrane separation unit. Meanwhile, the membrane-PSA hybrid process achieved a higher total H2 recovery (97.06%) than PSA-membrane hybrid process (94.35%) at the same H2 concentration of PSA feed gas (62.57%).
Co-reporter:Daishuang Zhang, Xiaoming Yan, Gaohong He, Le Zhang, Xinhong Liu, Fengxiang Zhang, Mengmeng Hu, Yan Dai and Sangshan Peng
Journal of Materials Chemistry A 2015 vol. 3(Issue 33) pp:16948-16952
Publication Date(Web):22 Jun 2015
DOI:10.1039/C5TA02913A
A novel integrally thin skinned asymmetric anion exchange membrane (ISAAEM) with sufficiently low ion exchange capacity (IEC) was proposed to improve the chemical stability of AEMs for vanadium flow batteries (VFBs). The ISAAEM with an IEC of 0.72 meq. g−1 showed low area resistance, slight VO2+ crossover and good electrochemical performance in VFBs.
Co-reporter:Rujie Wang, Xuemei Wu, Xiaoming Yan, Gaohong He, Zhengwen Hu
Journal of Membrane Science 2015 Volume 479() pp:46-54
Publication Date(Web):1 April 2015
DOI:10.1016/j.memsci.2014.12.054
•Excellent SPEEK/n-BuOH PEM was achieved with n-BuOH assisted self-organization.•Multiple hydrogen bonds facilitate the clustering of hydrophilic domains.•SPEEK/n-BuOH exhibits a proton conductivity as high as 0.314 S cm−1 at 80 °C.•Proton conductivities higher than Nafion at low relative humidity were obtained.Non-fluorinated proton exchange membranes are limited by poor proton conductivity due to weak phase separation and narrow hydrophilic channels. In this research, SPEEK membrane with high proton conductivity was fabricated by introducing self-organization inducer (n-BuOH). Multiple hydrogen bonds between SPEEK and n-BuOH facilitate the clustering of hydrophilic domains, and increase the ionic clusters from 1 nm to 3 nm. At 80 °C, SPEEK/n-BuOH membrane (IEC=1.5 mmol g−1) exhibits a proton conductivity as high as 0.314 S cm−1, yielding enhancements of 161% and 88% on pristine SPEEK and Nafion 115 membranes respectively. To the best of our knowledge, this is the highest proton conductivity among SPEEK based PEMs. Furthermore, SPEEK/n-BuOH exhibits proton conductivities even higher than Nafion at low relative humidity (from 40% to 90%). The modulus and tensile strength of SPEEK/n-BuOH are increased by 32% and 35% as well. Finally, a selectivity of 122×104 S s cm−3 is achieved for SPEEK/n-BuOH membrane, which is comparable to the reported highest value among SPEEK based PEMs (130×104 S s cm−3).
Co-reporter:Ning Zhang, Zhuanglin Shen, Cong Chen, Gaohong He, Ce Hao
Journal of Molecular Liquids 2015 Volume 203() pp:90-97
Publication Date(Web):March 2015
DOI:10.1016/j.molliq.2014.12.047
•We investigate the hydrogen bonding states of methanol/water binary mixture.•We examine the effect of hydrogen bonds on water self-diffusion.•Hydrophobic group of methanol contributes to the presence of isolated water.•Cluster analysis for water and methanol to reveal the cluster stabilitySelf-diffusion motion is strongly dependent on hydrogen bonding and temperature. In this work, the methanol/water mixtures of molalities from 1 to 5 m have been studied by molecular dynamics simulation. A definition of hydrogen bonding state is proposed to detailedly analyze the effects of the type and number of hydrogen bonds on the water self-diffusion. It is shown that most water molecules are in the hydrogen bonding state fkk, which means that one water molecule simultaneously hydrogen bonded to k water molecules with one hydrogen bond, respectively. Methanol prefers to produce isolated water molecules by the insertion of its hydrophobic group into the hydration shell of water. Besides, calculation of mean square displacements of water in different hydrogen bonding states shows that one water molecule with more hydrogen bonds diffuses more slowly. Pair energy of the hydrogen bonded molecules is also calculated to compare the attractive interactions of different types of hydrogen bonds. The hydrogen bonds between methanol and water present stronger attraction than that between water molecules. It indicates that increasing the concentration of methanol is conductive to restricting the water self-diffusion. Cluster analysis reveals that methanol cluster is more stable than water cluster in the binary mixtures. Thus high concentration of methanol enhances the blockage of the methanol cluster to water movement. These findings will lead us to further understand the mechanisms of water self-diffusion in the methanol/water mixture.
Co-reporter:Xuehua Ruan, Yan Dai, Lin Du, Xiaoming Yan, Gaohong He, Baojun Li
Separation and Purification Technology 2015 Volume 156(Part 2) pp:673-682
Publication Date(Web):17 December 2015
DOI:10.1016/j.seppur.2015.10.064
•Membranes competent for refining R23 are predicted by molecule critical property.•PDMS composite membranes fabricated by dip-coating are fit for R23 purification.•The prepared membrane behaves excellent with αR22/R23 = 3.2 and JR22 = 661 GPU.•4-stage membrane cascade is optimal to refine HFC-23 to a purity up to 99.5 mol%.•Specific cost for R23 refining is reduced to 67.7 $ t−1 with a 4-stage cascade.Fluoroform (HFC-23), the unavoidable byproduct of chlorodifluoromethane (HCFC-22) synthesis, is one of the most potent greenhouse gases. The general approach to incinerate the vent gas, though avoids the adverse environmental impacts, is a waste of HFC-23, which is valuable as refrigerant and plasma etchant. In this work, membrane process was coupled with distillation to separate high purity HFC-23 from the vent gas economically. Theoretical analysis and experimental tests were conducted to find the applicable membrane materials. The results indicated that the rubbery PDMS, with higher selectivity and gas permeation coefficients, was superior to the glassy PI for HFC-23 separation. PDMS thin-film composite membranes were prepared and characterized. In the actual permeation tests with industrial vent gas at 30 °C and 0.55 MPa, the as-prepared PDMS composite membranes behaved with selectivity αF22/F23 = 3.2 and permeation rate JF22 = 661 GPU, respectively. Afterwards, the cascaded membrane systems with different stage number were studied by process simulation and their economic feasibility was analyzed. Briefly according to the economic data, the 4-stage cascade structure is the optimal configuration to couple with distillation unit. For a 50 kt/a synthesis plant, the 4-stage process can efficiently refine HFC-23 to a purity as high as 99.5 mol%, with a specific cost of 70 USD t−1 and an extra gross profit of 3.8 × 106 USD a−1. However, taking the process complexity into account, the 3-stage cascaded process, although exhibited slightly lower economic performance, is more suitable in industry. Overall, our studies have revealed that coupling PDMS membrane unit with distillation is a feasible and promising technique to separate high purity HFC-23 efficiently and economically in the HCFC-22 synthesis industries.
Co-reporter:Xiaoming Yan;Xuemei Wu;Shuang Gu;Xue Gong;Jay Benziger
Journal of Applied Polymer Science 2015 Volume 132( Issue 5) pp:
Publication Date(Web):
DOI:10.1002/app.41404
ABSTRACT
A mixed methanesulfonic acid/sulfuric acid solvent based chlromethylation of poly(ether ether ketone) (PEEK) is described. Methanesulfonic acid is the solvent, sulfuric acid is the catalyst, and chloromethyl octyl ether (CMOE) is the chloromethylating reagent. 1H-NMR spectra confirmed the successful synthesis of chloromethylated PEEK (CMPEEK). The effects of polymer concentration, catalyst/polymer ratio, and reaction temperature on the rate of PEEK chloromethylation were investigated. In order to minimize crosslinking, the PEEK concentration must be kept very low (< 2%). The reaction rate increases with increased catalyst/polymer ratio and reaction temperature. The activation energy of PEEK chloromethylation is 30.9 kJ mol−1. The extent of reaction for the new route is more easily controllable as compared with the previous sulfuric acid based route. The reaction rate constant at 25°C for the new route is 1.29 h−1 which is lower than that for chloromethylation by concentrated sulfuric acid at −10°C (rate constant 1.88 h−1). As a result, the degree of chloromethylation of CMPEEK can be easily controlled at room temperature using this mixed solvent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41404.
Co-reporter:Mo Li, Xiangcun Li, Xinhong Qi, Fan Luo, and Gaohong He
Langmuir 2015 Volume 31(Issue 18) pp:5190-5197
Publication Date(Web):April 19, 2015
DOI:10.1021/acs.langmuir.5b00800
The preparation of nonspherical magnetic core–shell nanostructures with uniform sizes still remains a challenge. In this study, magnetic iron oxide@SiO2–Au@C particles with different shapes, such as pseduocube, ellipsoid, and peanut, were synthesized using hematite as templates and precursors of magnetic iron oxide. The as-obtained magnetic particles demonstrated uniform sizes, shapes, and well-designed core–shell nanostructures. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) analysis showed that the Au nanoparticles (AuNPs) of ∼6 nm were uniformly distributed between the silica and carbon layers. The embedding of the metal nanocrystals into the two different layers prevented the aggregation and reduced the loss of the metal nanocrystals during recycling. Catalytic performance of the peanut-like particles kept almost unchanged without a noticeable decrease in the reduction of 4-nitrophenol (4-NP) in 8 min even after 7 cycles, indicating excellent reusability of the particles. Moreover, the catalyst could be readily recycled magnetically after each reduction by an external magnetic field.
Co-reporter:Xiangcun Li, Fan Luo, and Gaohong He
Langmuir 2015 Volume 31(Issue 18) pp:5164-5173
Publication Date(Web):April 20, 2015
DOI:10.1021/la505032a
Double-shelled C/SiO2 hollow microspheres with an outer nanosheet-like silica shell and an inner carbon shell were reported. C/SiO2 aerosol particles were synthesized first by a one-step rapid aerosol process. Then the solid silica layer of the aerosol particles was dissolved and regrown on the carbon surface to obtain novel C/SiO2 double-shelled hollow microspheres. The new microspheres prepared by the facile approach possess high surface area and pore volume (226.3 m2 g–1, 0.51 cm3 g–1) compared with the original aerosol particles (64.3 m2 g–1, 0.176 cm3 g–1), providing its enhanced enzyme loading capacity. The nanosheet-like silica shell of the hollow microspheres favors the fixation of Au NPs (C/SiO2/Au) and prevents them from growing and migrating at 500 °C. Novel C/C and C/Au/C (C/Pt/C) hollow microspheres were also prepared based on the hollow nanostructure. C/C microspheres (482.0 m2 g–1, 0.92 cm3 g–1) were ideal electrode materials. In particular, the Au NPs embedded into the two carbon layers (C/Au/C, 431.2 m2 g–1, 0.774 cm3 g–1) show a high catalytic activity and extremely chemical stability even at 850 °C. Moreover, C/SiO2/Au, C/Au/C microspheres can be easily recycled and reused by an external magnetic field because of the presence of Fe3O4 species in the inner carbon shell. The synthetic route reported here is expected to simplify the fabrication process of double-shelled or yolk–shell microspheres, which usually entails multiple steps and a previously synthesized hard template. Such a capability can facilitate the preparation of various functional hollow microspheres by interfacial design.
Co-reporter:Xuemei Wu, Wanting Chen, Xiaoming Yan, Gaohong He, Junjun Wang, Ying Zhang and Xiaoping Zhu
Journal of Materials Chemistry A 2014 vol. 2(Issue 31) pp:12222-12231
Publication Date(Web):01 May 2014
DOI:10.1039/C4TA01397B
Poly(ether ether ketone) (PEEK) with multiple quaternary ammonium groups on pendent side chains is synthesized through the chloromethylation di-quaternization route, using bi-functional 1,4-diazabicyclo[2,2,2]octane (DABCO) as quaternization reagent. The materials are made into tough and transparent anion exchange membranes (AEMs) by solvent casting. The purpose is to promote efficient hydroxide ion conductive channels, which are particularly important and challenging to improve hydroxide conductivity of AEMs due to the inherently low mobility of hydroxide ions. Transmission electron microscopy (TEM) images show ionic clusters of bigger size scattering in the di-quaternized membranes compared with the mono-quaternized membranes. Given similar ion exchange capacities (IECs), the di-quaternized membranes exhibit much higher values of effective hydroxide ion mobility (∼3.5 × 10−4 cm2 s−1 V−1) than the mono-quaternized membranes (∼1.7 × 10−4 cm2 s−1 V−1). The structure of multiple quaternary ammonium groups on the pendent side chain promotes hydrophilic–hydrophobic micro-phase separation and efficient hydroxide ion conductive channels in the membranes. As a result, hydroxide conductivity of the di-quaternized membranes is about 2 to 3 fold higher than that of the mono-quaternized membranes with similar IEC, exhibiting a high value of about 35.3 mS cm−1 at 25 °C. At a certain IEC, the di-quaternized membranes have fewer pendent side chains on the polymer backbone, which also benefits the mechanical and chemical stabilities of the AEMs.
Co-reporter:Xuemei Wu, Gaohong He, Xiangcun Li, Fei Nie, Xiaoming Yan, Lu Yu, Jay Benziger
Journal of Power Sources 2014 Volume 246() pp:482-490
Publication Date(Web):15 January 2014
DOI:10.1016/j.jpowsour.2013.07.108
•Proton conductivity at low RH is improved by interpenetrating CrPSSA into SPEEK PEM.•At RH 25% proton conductivity of SPEEK/CrPSSA 40 reaches 10−3 S cm−1.•Percolation thresholds of around 0.2 indicate elongated clusters in sIPN membranes.•It is easy for elongated clusters to swell and interconnect at low RH.•The sIPN membranes exhibit good miscibility and can be stable up to 250 °C in N2.Crosslinked poly (styrene sulfonic acid) (CrPSSA) is incorporated into sulfonated poly (ether ether ketone) (SPEEK) through the semi-interpenetrating polymer networks (sIPNs) method to improve proton conductivity of SPEEK proton exchange membranes (PEMs) at low relative humidity (RH). Thermogravimetric analysis indicates that the SPEEK/CrPSSA sIPN membrane can be stable up to 250 °C in N2. A single glass transition temperature (Tg) of the sIPN measured by differential scanning calorimetric measurements suggests good miscibility of the CrPSSA and SPEEK. At fixed RH the proton conductivity of the sIPN membranes increases as more CrPSSA is incorporated into SPEEK membranes. The sIPN membrane with 40 wt. % CrPSSA has a proton conductivity of 10−3 S cm−1 at 25% RH, which comparable to that of Nafion115 and is 2 orders of magnitude higher than that of the pristine SPEEK membranes (10−5 S cm−1 at RH 50%). The percolation threshold for proton conduction occurs at lower hydrophilic volume fractions with the increasing content of CrPSSA, suggesting different packing behavior of –SO3H groups in the SPEEK/CrPSSA sIPN membranes as compared with SPEEK and Nafion® membranes.
Co-reporter:Xuemei Wu, Gaohong He, Lu Yu, and Xiangcun Li
ACS Sustainable Chemistry & Engineering 2014 Volume 2(Issue 1) pp:75
Publication Date(Web):November 10, 2013
DOI:10.1021/sc400329s
The possibility of using a nonfluorinated proton exchange membrane for H2/CO2 separation in an electrochemical hydrogen pump has been evaluated for the purpose of reducing cost. A sulfonated poly(ether ether ketone) (SPEEK)/cross-linked poly(styrene sulfonic acid) (CrPSSA) semi-interpenetrating polymer network membrane exhibits a much higher proton conductivity (0.09 S cm–1 at 80 °C) and humidity sensitivity as compared with the pristine SPEEK membrane. Performance of the hydrogen pump with the sIPN membrane is investigated in different CO2 contents. The limiting currents are around 0.5–0.6 A and decrease with an increase in CO2 content, which indicates the transition of the dominant resistance from ohmic resistance to mass transport resistance. Energy efficiency of the SPEEK/CrPSSA-based hydrogen pump is around 30%, which is only slightly lower than that of the Nafion-based hydrogen pump (around 40%) reported in the literature. The results presented here suggest that a nonfluorinated membrane-based hydrogen pump could be promising for hydrogen purification.Keywords: Electrochemical hydrogen pump; Hydrogen purification; Interpenetrating polymer networks; Proton exchange membranes; Sulfonated poly (ether ether ketone)
Co-reporter:Xiangcun Li, Wenji Zheng, Gaohong He, Rui Zhao, and Dan Liu
ACS Sustainable Chemistry & Engineering 2014 Volume 2(Issue 2) pp:288
Publication Date(Web):October 22, 2013
DOI:10.1021/sc400328u
TiO2 nanoparticles with controlled morphology and high photoactivity were prepared using a microemulsion-mediated hydrothermal method in this study, and the particles were characterized by means of TEM, XRD, BET, and BJH analysis. As the hydrothermal temperature is elevated, mean pore diameter, crystalline size, and crystallinity of the particles increase gradually, while the surface area decreases significantly, and the morphology changes from a spherical into a rod-like shape. The morphology transition mechanism of the TiO2 crystal has been put forward based on a decrease in intensity of the microemulsion interface and an increase in collision efficiency between droplets with increasing the hydrothermal temperature. The photocatalytic activity of the TiO2 particles synthesized at 120–200 °C is relatively low due to their weak crystallinity, though they have high surface area of 146–225 m2/g and small crystalline size of 6–10 nm. However, the TiO2 samples prepared at 250–350 °C with low surface area (28–90 m2/g) exhibit high activity on the degradation of Rhodamine B (RhB), which is comparable or higher than that of the commercial P-25. The reason is ascribed to their high crystallinity that determines material activity in this temperature region. This study reveals that the effects of the surface area, crystallinity, and crystalline size on TiO2 activity are interdependent, and the balance between these factors is important for improving the photoactivity of the catalyst.Keywords: Crystallinity; Hydrothermal; Microemulsion; Photoactivity; TiO2
Co-reporter:Wenji Zheng, Xiangcun Li, Chunxu Dong, Xiaoming Yan and Gaohong He
RSC Advances 2014 vol. 4(Issue 85) pp:44868-44871
Publication Date(Web):04 Sep 2014
DOI:10.1039/C4RA07886A
A visible light detector can be fabricated using a coaxial polypyrrole/TiO2 nanorod composite. Based on the composite, the detector exhibits high responsivity up to 0.45 A W−1, impressive stability and excellent linear dependence of the photoresponse on visible light intensity. All of these properties make the polypyrrole/TiO2 nanorod composite very competitive and highly applicable in visible light detection.
Co-reporter:Wenji Zheng, Xiangcun Li, Gaohong He, Xiaoming Yan, Rui Zhao and Chunxu Dong
RSC Advances 2014 vol. 4(Issue 41) pp:21340-21346
Publication Date(Web):11 Apr 2014
DOI:10.1039/C4RA01553C
Hierarchical TiO2 nanorod/nanoparticle composites were successfully prepared by TiCl4 modification of vertically aligned TiO2 nanorod (NR) arrays. After the hydrolysis of TiCl4 at room temperature, TiO2 nanoparticles (NPs) were deposited on the surface of TiO2 NRs. Morphology and structure analysis demonstrated that the TiO2 NPs were distributed around the entire surface of TiO2 NRs due to the easy permeation of TiCl4 solution between the NR space. Moreover, the high concentration of TiCl4 and long reaction time are favorable for the generation of more TiO2 NPs, which correspondingly increases the surface area of the composite to a large extent. Compared with most reported TiO2-based UV photodetectors (PDs), the present TiO2 NR/NP composite-based PDs simultaneously exhibit an extremely high response and a relatively fast response speed. The maxima of responsivity and response speed, which are 1973 A W−1 and 0.47 s (rise time) and 1.02 s (decay time), respectively, are obtained from the sample of TiO2 NR/NP-0.4 M-72 h. The fast and high photoresponses are ascribed to the large surface area provided by TiO2 NPs, the well-defined electron transport pathway offered from TiO2 NRs and the homojunction formed at the interface between them. Moreover, together with the high responsivity and the relatively fast response speed, significant UV light selectivity and a very good linear relationship between a photoresponse and the UV light intensity suggest that the present UV PDs are very competitive and highly applicable in UV light detection.
Co-reporter:Xuehua Ruan, Gaohong He, Baojun Li, Junli Xiao, Yan Dai
Separation and Purification Technology 2014 Volume 124() pp:89-98
Publication Date(Web):18 March 2014
DOI:10.1016/j.seppur.2014.01.014
Co-reporter:Chunxu Dong, Gaohong He, Wenji Zheng, Tengfei Bian, Mo Li, Dawei Zhang
Materials Letters 2014 Volume 134() pp:286-289
Publication Date(Web):1 November 2014
DOI:10.1016/j.matlet.2014.07.110
•Mg(OH)2 nanobars of about 2 μm length could not kill E. coli.•UV illumination for 4 h may accelerate the antibacterial behavior of Mg(OH)2.•Mg2+ in the sample culture increased a lot after the antibacterial test.•Nano Mg(OH)2 would enter into cells through endocytosis and release OH−.•The intracellular high pH (pH of ~10) may lead to cell death.Recently, Mg(OH)2 nanoparticles were reported to be efficient antibacterial agent. In this work, the antibacterial behavior of Mg(OH)2 nanoparticles against Escherichia coli was further investigated. Results indicate that the antibacterial mechanism of Mg(OH)2 nanoparticles is different from the existing ones of metal-based compounds. It is found that the Mg2+ increased a lot in the sample culture after the antibacterial test. Mg(OH)2 nanobars of about 2 μm length did not show any antibacterial property, and the ultraviolet illumination for certain time can accelerate the antibacterial behavior of Mg(OH)2 nanoplatelets. A novel possible antibacterial mechanism of Mg(OH)2 nanoparticles was consequently proposed. When contacting directly with a bacterial cell, Mg(OH)2 nanoparticles would enter into the cell through endocytosis and accumulate in vivo. Since there is over 70% water inside the cell, the Mg(OH)2 nanoparticles would inevitably dissolve and OH− would be released until an equilibrium is reached (pH of ~10). Therefore, the intracellular high pH would lead to cell death.
Co-reporter:Dan Liu;Xin-An Zeng;Da-Wen Sun;Xiangcun Li
Polymer Composites 2014 Volume 35( Issue 7) pp:1388-1394
Publication Date(Web):
DOI:10.1002/pc.22791
Reverse water/oil (w/o) microemulsions composed of epoxy resin (EP) (the oil phase) and nonionic surfactant and ammonia aqueous solutions (the water phase) were used in the synthesis of SiO2/EP nanocomposites. The stability of reverse microemulsion was evaluated by measuring water solubilization of the microemulsion. Effects of surfactant type and content, ammonia concentration and temperature on the water solubilization were systematically investigated. Higher water solubilization capacity was obtained by nonionic surfactant TX-100 compared with other two surfactants, Span-80 and Tween-80. Ammonia concentration of 5 wt% and preparation temperature at 35°C were favorable for forming a stable microemulsion and enabling the subsequent hydrolysis and condensation reaction of inorganic precursor tetraethoxysilane (TEOS). SiO2/ epoxy nanocomposites were prepared via in situ polymerization of TEOS within the nanoscale reverse microemulsion “water pool”. FTIR, SEM, and universal testing machine were used to characterize the structural and mechanical properties of the composite. The results revealed that the optimal mechanical properties were obtained at 3 wt% TEOS content. Compared with neat epoxy resin, the tensile and flexural strength of the composite were 40% and 12% higher, respectively. The formation of the silica structure in the hybrid was investigated with FTIR. The SEM and optical observations showed a ductile fracture morphology and good miscibility between inorganic and organic phases. POLYM. COMPOS., 35:1388–1394, 2014. © 2013 Society of Plastics Engineers
Co-reporter:Zhengwen Hu;Shuang Gu;Yuanfa Liu;Xuemei Wu
Journal of Applied Polymer Science 2014 Volume 131( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/app.39852
ABSTRACT
To produce a composite membrane with high conductivity and low permeability, SPPESK with a degree of sulfonation of 101% was carefully selected for the preparation of montmorillonite (MMT)-reinforced SPPESK using solution intercalation. The fundamental characteristics such as water uptake, swelling ratio, proton conductivity, methanol permeability, and mechanical properties of the composite membranes were studied. Water uptake is improved when organic MMT (OMMT) loading increase. The composite membranes with CTAB-MMT loading of 4–0.5% show 0.143–0.150 S cm−1 proton conductivity at 80°C, which approaches the value of Nafion112. In addition, methanol permeability was decreased to 6.29 × 10−8 cm2 s−1 by the addition of 6 wt % OMMT. As a result, the SPPESK-MMT composite membrane is a good candidate for use in direct methanol fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39852.
Co-reporter:Fei Nie;Yuanfa Liu;Wei Zhao ;Jia Ju
Journal of Applied Polymer Science 2014 Volume 131( Issue 22) pp:
Publication Date(Web):
DOI:10.1002/app.41082
ABSTRACT
Polyimide (PI) as a typical glassy polymer material was investigated by molecular simulation to reveal the relationship between polymer molecular structure and its gas separation properties. The influences of van der waals volume (Vw) on CO2 permselectivity of PI polymers (with four kinds of backbone substitute groups and a series of side substitute groups from small to large volume) and Vw was proposed as an intermediate to establish the relationship between the substitute group and permselectivity. The results show that the CO2 permeability (P) simply increases and CO2/N2 selectivity (S) decreases with the increasing Vw of side substitute groups. The linear fitline of P-Vw is much suitable to describe and predict the effect of the increasing Vw of side substitute group on improving permeability by analyzing the experimental and calculated CO2 permeability. The increasing Vw of backbone substitute group can slow down the increasing of CO2 permeability, but result in the decreasing first and then recovering to the original level. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41082.
Co-reporter:Xiaoming Yan, Shuang Gu, Gaohong He, Xuemei Wu, Wenji Zheng, Xuehua Ruan
Journal of Membrane Science 2014 466() pp: 220-228
Publication Date(Web):
DOI:10.1016/j.memsci.2014.04.056
Co-reporter:Rujie Wang;Xiaoming Yan;Xuemei Wu;Lin Du;Zhengwen Hu ;Ming Tan
Journal of Polymer Science Part B: Polymer Physics 2014 Volume 52( Issue 16) pp:1107-1117
Publication Date(Web):
DOI:10.1002/polb.23540
ABSTRACT
Modification of proton conductive channels (PCCs) in Nafion has been achieved with the assistance of 3, 4-dimethylbenzaldehyde (DMBA). During annealing, ionic clusters develop from small isolated spheres (1.72 nm) to wide continuous channels (5.15 nm), and the crystallinity of Nafion/DMBA membranes is also improved from 17% to 32% as shown by X-ray diffraction. Molecular dynamic simulation reveals that hydrogen bonding and hydrophobic interaction between DMBA and Nafion work synergistically to achieve better phase separation. The morphology–property relationship shows that, versus various PCCs width, the corresponding proton conductivities vary greatly from 0.079 to 0.139 S/cm at 80 °C. By carefully tuning the width of PCCs, the proton conductivity shows an improvement of 22–34% as compared with pristine Nafion. A significant enhancement on the maximum power density is achieved for the membrane electrode assembly on Nafion/DMBA-8h (as high as 1018 mW/cm−2), yielding an enhancement of 39% on pristine Nafion-8h (730 mW/cm−2). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 52, 1107–1117
Co-reporter:Wenhua Shi, Gaohong He, Hongjing Liu, Jia Ju, Tonghua Wang, Xiangcun Li, Fei Nie
The Journal of Supercritical Fluids 2014 Volume 85() pp:151-158
Publication Date(Web):January 2014
DOI:10.1016/j.supflu.2013.11.009
•The PEI membrane formed in ScCO2 was proposed to prepare an affinity matrix.•Residual NMP in the membrane was nearly zero, which was measured by a GC–MS system.•Pore size distribution of the membrane was narrow.•The PEI-chitosan-CB affinity membrane showed a high tensile strength of 11.58 MPa.•The affinity membrane showed an adsorption capacity of 33.9 mg/g membrane to BSA.Polyetherimide (PEI) microporous membranes with uniform cellular structure, high porosity, and narrow pore size distribution were formed by supercritical CO2 (ScCO2) phase inversion method, and the membrane was modified to be a matrix for the preparation of affinity membrane due to its low solvent residue and appropriate porous structure. The effects of ScCO2 temperature and pressure on the morphology and pure water flux of the membrane were investigated. The membrane prepared at 24 MPa and 45 °C with a large mean cell diameter of 6.0 μm, high porosity of 73%, narrow pore size distribution and a pure water flux of 56 L/(m2 h bar) was coated with chitosan to improve its hydrophilicity and coupled with Cibacron Blue F3GA (CB) as a special ligand to form an affinity membrane (PEI-coated chitosan-CB membrane). The PEI-coated chitosan-CB membrane showed a high adsorption capacity of 33.9 mg/g membrane to bovine serum albumin and was higher than most of affinity membranes. Moreover, the tensile strength of PEI-coated chitosan-CB membrane was 11.58 MPa and was much higher than those of affinity membranes. This work demonstrates that ScCO2 phase inversion method is a potential method to prepare an affinity matrix.
Co-reporter:Fei Nie;Wei Zhao;Jia Ju;Yuanfa Liu;Yan Dai
Journal of Polymer Research 2014 Volume 21( Issue 1) pp:
Publication Date(Web):2014 January
DOI:10.1007/s10965-013-0319-x
Polyethylene glycol (PEG) as a promoting material for CO2 separation performance of a composite membrane is introduced into the polytrifluoropropylmethylsiloxane (PTFPMS) network to form a blend selective layer coated on a porous polyetherimide (PEI) support membrane. The maximum blend ratio of PEG to PTFMS in mass is determined for PEG-400, PEG-600, and PEG-1000 at 0.5, 0.2 and 0.2 from the blend solution status observed by an optical microscope. The miscibility of PEG and PTFPMS is verified from one peak of the blend film in DSC characterization. Furthermore, the interaction between PEG and PTFPMS is van der Waals force from the decreasing strength of ether group in ATR-FTIR analysis. The stability of the PEG/PTFPMS blend composite membrane is investigated with pure N2, O2, and CO2 permeation experiments under the transmembrane pressure difference up to 1.0 MPa. The N2 permeation rate of the PEG400/PTFPMS blend composite membrane with a blend ratio of 0.2 is 2.11 GPU, while the O2/N2 and CO2/N2 selectivities are improved to 2.67 and 26.67, respectively, which are higher than those of pure PTFPMS composite membrane that is 2.2 and 13.79, respectively.
Co-reporter:Ming Tan;Yan Dai;Rujie Wang
Frontiers of Chemical Science and Engineering 2014 Volume 8( Issue 3) pp:312-319
Publication Date(Web):2014 September
DOI:10.1007/s11705-014-1434-x
The ternary phase diagrams of polyetherimide (PEI)/N,N-dimethylacetamide (DMAc) with H2O and BuOH as non-solvent were simulated using solubility parameter and Flory-Huggins theory. The phase diagrams show that 5.5% H2O/BuOH system containing 5% BuOH and 0.5% H2O, or 6.5% H2O/BuOH system containing 6.2% BuOH and 0.3% H2O is required to induce liquid-liquid demixing for 20 wt-% PEI/DMAc casting solution. Therefore, BuOH can enhance the phase separation of the PEI casting solution and hereby induce higher porosity of the membrane, and the diffusion of BuOH into the water coagulation bath causes larger pore size easily compared with DMAc. Our predictions that the membrane pure water flux first increases then decreases, and the rejection ratio of bovine serum albumin decreases with the increasing concentration of BuOH were validated by the experiments using the prepared membranes.
Co-reporter:Mo Li;Xiaobin Jiang
Frontiers of Chemical Science and Engineering 2014 Volume 8( Issue 2) pp:233-239
Publication Date(Web):2014 June
DOI:10.1007/s11705-014-1408-z
Membrane separation technology is a possible breakthrough in post-combustion carbon dioxide capture process. This review first focuses on the requirements for CO2 separation membrane, and then outlines the existing competitive materials, promising preparation methods and processes to achieve desirable CO2 selectivity and permeability. A particular emphasis is addressed on polyimides, poly (ethylene oxide), mixed-matrix membrane, thermally-rearranged polymer, fixed site carrier membrane, ionic liquid membrane and electrodialysis process. The advantages and drawbacks of each of materials and methods are discussed. Research threads and methodology of CO2 separation membrane and the key issue in this area are concluded
Co-reporter:Xiangcun Li, Jiasi Sun, Gaohong He, Guanglan Jiang, Yi Tan, Bing Xue
Journal of Colloid and Interface Science 2013 Volume 411() pp:34-40
Publication Date(Web):1 December 2013
DOI:10.1016/j.jcis.2013.08.052
•Novel hierarchical macroporous PPy–TiO2 composite nanostructures.•Synergetic interaction between PPy and TiO2 for effective charge pair separation.•Improved photoactivity for degradation of MB under simulated sun light irradiation.•High H2O2 detecting sensitivity with appropriate PPy content in composites.•Dispersed PPy nanoparticles by etching the composites with HF acid.Macroporous polypyrrole (PPy)-TiO2 composites were prepared by in situ oxidative polymerization of pyrrole in the macropores of TiO2. The formation mechanism of the PPy nanoparticles, including nucleation and further growth, was proposed by studying the particle growth process with increasing reaction time. The special growth process favors the formation of good cohesion and stabilized interface between the inorganic and organic phases. The conversion ratio of pyrrole monomer is in the range of 65.3–97.5%, and PPy content in the composites can reach as high as 21.04% with well preservation of the macroporous framework. Furthermore, dispersed PPy particles of ∼100 nm in size can be obtained by etching the composites in HF acid, which is smaller than the PPy particles synthesized in the absence of the TiO2 template due to the pore-confinement effect. The composites show improved photoactivity on degradation of dye under simulated sunlight irradiation and electrocatalytic activity toward the detection of H2O2 in 0.1 M phosphate buffer solution. Synergetic interaction between the two components and the porous structure is considered to be responsible for the enhanced properties of the new composites.Graphical abstract
Co-reporter:Rui Zhao, Xiaodan Zhang, Jiping Xu, Yang Yang and Gaohong He
RSC Advances 2013 vol. 3(Issue 45) pp:23178-23183
Publication Date(Web):23 Sep 2013
DOI:10.1039/C3RA43300E
Different from most ionic diodes which use water as the medium, in this paper, we reported flexible solid state ionic diodes without water during the fabrication and operation. The ionic diodes were fabricated by sandwiching a PEO-doped separator sheet between two paper sheets, respectively doped with AgNO3–polyethylene oxide (PEO) and KI–PEO electrolyte. The working mechanism of the solid diodes was based on the different electrochemical and participation reactions under different bias. The rectification ratio of the diode devices could reach 46 under an input AC voltage between ±1 V. The devices exhibited good flexibility and showed stable rectifying behavior after more than 800 bending cycles. The effects of plasticizer on the rectifying performances of diodes were systematically studied. The stability of the devices fabricated with or without plasticizer in PEO was investigated. The results showed that there was a trade-off between rectifying performance and stability.
Co-reporter:Xiaobin Jiang, Jingkang Wang, Baohong Hou, and Gaohong He
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 45) pp:15685-15701
Publication Date(Web):2017-2-22
DOI:10.1021/ie402182f
The application of fractal porous media (FPM) theory in melt crystallization is a novel concept to be developed extensively, which has received wide attention in recent years. The primary advantage of FPM theory is the ability to describe the complex, random structure of porous crystal layers with fewer parameters. This review will introduce aspects of the property analysis of porous crystal layers grown in the heterogeneous thermal field. For the first time, the existing flow model of FPM theory will be outlined and an overview of the general issues, model modification, and validation of the separation process in melt crystallization will be discussed in detail. Kinetic and model research on separation evaluation and optimized operation will be mentioned to unfold the promising application field. Finally, the paper will conclude with perspectives on the future research directions, key challenges, and issues in this area.
Co-reporter:Xiaoming Yan, Yongdong Wang, Gaohong He, Zhengwen Hu, Xuemei Wu, Lin Du
International Journal of Hydrogen Energy 2013 Volume 38(Issue 19) pp:7964-7972
Publication Date(Web):27 June 2013
DOI:10.1016/j.ijhydene.2013.04.108
•QAPEIs were successfully synthesized through homogeneous quaternization.•QAPEIs show good solubility in polar solvents.•QAPEI/PTFE composite membranes exhibit high hydroxide conductivity.•QAPEI/PTFE composite membranes show good thermal stability.A series of soluble quaternized polyetherimides (QAPEIs) have been successfully synthesized by homogeneous quaternization in trimethylamine aqueous solution. 1H NMR spectra confirm the successful synthesis of QAPEI. The QAPEIs exhibit good solubility in membrane-preparation solvents, making it possible to prepare the QAPEI composite membrane. Novel composite hydroxide exchange membranes have been prepared by incorporating QAPEIs with polytetrafluoroethylene (PTFE) membranes. The SEM images, gas permeation measurements and FTIR spectra show that the QAPEI is successfully filled in PTFE membrane and the resulted composite membrane is dense and smooth. The ion exchange capacity of composite membranes ranges from 0.35 to 0.58 mmol g−1. The composite membranes have appropriate water uptake (≤154%) and moderate swelling ratio (≤42%) even at 60 °C. The hydroxide conductivity of the composite membrane reaches 11.9 mS cm−1 at 20 °C that increases to 35.2 mS cm−1 at 60 °C. TGA curve shows that the composite membrane possesses high thermal stability (TOD: 210 °C). All these properties indicate that the QAPEI/PTFE composite membranes are good candidates for use as HEMs in HEM fuel cells.
Co-reporter:Danmin Xing, Gaohong He, Zhongjun Hou, Pingwen Ming, Shufan Song
International Journal of Hydrogen Energy 2013 Volume 38(Issue 20) pp:8400-8408
Publication Date(Web):9 July 2013
DOI:10.1016/j.ijhydene.2013.04.084
•The Nafion/PTFE composite membrane was fabricated by solution-spray process.•The Nafion/PTFE composite membrane was evaluated for fuel cell application.•The Nafion/PTFE composite membrane shows high strength and low swelling.•The 20 kW stack with Nafion/PTFE composite membranes has good performance.The Nafion/polytetrafluoroethylene (Nafion/PTFE) composite membrane is fabricated by a solution-spray process. The performance and morphology of the composite membrane are studied in terms of the mechanical properties, conductivity, and permeability. The results of TEM and X-ray studies show that the morphologies of crystalline and ion cluster of the perfluorosulfonated acid (PFSA) in composite membrane are apparently similar to that of Nafion® NR211 membrane. The composite membrane has higher stiffness and strength and lower swelling than that of Nafion® NR211. The conductivity at 85 °C of 0.375 S cm−1 is relatively high in comparison to that of 0.300 S cm−1 for Nafion® NR211. The 20 kW stack with the composite membranes is evaluated. The mean single cell voltage is 0.67 V @1000 mA cm−2. The stack has behaved performance uniformity and steadily operated under low humidifying condition. In consideration of the integration of complex structure and perfect morphology, the solution-spray process is feasible for composite proton exchange membrane manufacture.
Co-reporter:WenJi Zheng;XiangCun Li;XiaoMing Yan
Science China Technological Sciences 2013 Volume 56( Issue 11) pp:2642-2645
Publication Date(Web):2013 November
DOI:10.1007/s11431-013-5354-7
Vertically aligned TiO2 nanorods arrays were successfully synthesized on FTO glass by wet-chemical method. Based on polystyrene sulfate (PSS) functionalized TiO2 nanorods arrays, a sandwich-structured hybrid UV photodetector was fabricated. The photo-to-dark current ratio of the device increases by more than 3 orders of magnitude with typical case, while the dark current is about 10 nA at 1 V bias. The high photoresponse together with the low dark current could probably contribute a large photocurrent and low-power application. The high performance of the hybrid material and facile low-cost fabrication of the UV detector make the devices promising for large-area UV photodetection applications.
Co-reporter:Wenhua Shi, Gaohong He, Wei Zhao, Lingling Zhang, Lin Du, Yongdong Wang, Xiaochen Qin
The Journal of Supercritical Fluids 2013 Volume 83() pp:6-14
Publication Date(Web):November 2013
DOI:10.1016/j.supflu.2013.08.005
Co-reporter:Wei Zhao, Gaohong He, Fei Nie, Lingling Zhang, Hongchao Feng, Hongjing Liu
Journal of Membrane Science 2012 Volumes 411–412() pp:73-80
Publication Date(Web):1 September 2012
DOI:10.1016/j.memsci.2012.04.016
Membrane liquid loss of supported ionic liquid membranes (SILMs) under high cross-membrane pressure difference (Δp) is an urgent issue in gas separation. In our research, it was found that the even serious loss of the membrane liquid might not lead to the degradation of SILMs. To explore the underlying membrane liquid loss mechanism of SILMs, SILMs were prepared with 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) immobilized in polyethersulfone (PES), nylon 6 (N6), and polyvinylidene fluoride (PVDF) microporous membranes. The membrane liquid loss behaviors of the SILMs were investigated in terms of gas separation performance and the weight loss of membrane liquid (ML loss). The PES SILM has the least ML loss owing to the less interconnected network, small maximum pore size of the membrane, as well as the great interaction of PES with [bmim][BF4]. Membrane compression was proposed as one of the main reasons of the membrane liquid loss of the SILMs, which did not lead to the degradation of the PES SILM because of the reduction of the pore diameter and the thickness of the membrane. A mathematical model was established to evaluate the dimensional changes of the PES SILM caused by compression. The membrane thickness is reduced and the pore size and porosity are also decreased, when Δp is increased only from 0.1 to 0.3 MPa.Highlights► Membrane liquid loss mechanism of supported ionic liquid membrane (SILM) is studied. ► SILM compression under operating pressure difference leads to membrane liquid loss. ► Membrane liquid loss due to the compression cannot result in SILM degradation. ► A mathematical model is established to evaluate the dimension changes of SILM. ► When SILM is compressed, its pore size, porosity, and thickness are decreased.
Co-reporter:Ming Tan, Gaohong He, Xiangcun Li, Yuanfa Liu, Chunxu Dong, Jinghai Feng
Separation and Purification Technology 2012 Volume 89() pp:142-146
Publication Date(Web):22 March 2012
DOI:10.1016/j.seppur.2012.01.011
In this study, the preparation process of polydimethylsiloxane (PDMS)/ceramic composite membrane was successfully modeled by the hybrid models which employed backpropagation neural network (BPNN) to predict the effects of preparation conditions on pervaporation performances of membranes and used genetic algorithm (GA) to choose the initial connection weights and biases of BPNN. The PDMS concentration, crosslinking agent concentration and dip-coating time were taken as inputs, flux of ethanol and selectivity of ethanol/water were outputs, and trial-and-error method was used to determine the architectures of the hybrid models. Using these models, the detailed relationships between the preparation conditions and the membrane performances were established. Connection weight analyses show that each preparation condition almost has the same influence on the membrane flux and selectivity. Excellent agreements between the predictions of the hybrid models and the experiments validate that the hybrid models have sufficient accuracy. Furthermore, the results predicted by the hybrid models were compared with those predicted by the response surface methodology (RSM) models which were widely used in the optimization of nonlinear relationships. It is found that the standard deviations of both the training and the predicting data obtained by the hybrid models are much smaller than those by the RSM models. Hence, the hybrid models can be used to design the preparation conditions to obtain desired membrane performances in the preparation of pervaporation membranes.Highlights► GA is employed to choose the initial connection weights and biases of BPNN. ► The model can calculate the relative importance of each preparation condition. ► Effects of preparation conditions on membrane performances are predicted. ► The model can design preparation conditions to obtain desired membrane performance.
Co-reporter:Lin Du, Xiaoming Yan, Gaohong He, Xuemei Wu, Zhengwen Hu, Yongdong Wang
International Journal of Hydrogen Energy 2012 Volume 37(Issue 16) pp:11853-11861
Publication Date(Web):August 2012
DOI:10.1016/j.ijhydene.2012.05.024
In order to increase both of the water uptake and conductivity, the proton exchange membranes were fabricated by sulfonated poly(ether ether ketone) (SPEEK) doped with varied contents of silica sulfuric acid (SSA) which is obtained by treating SiO2 nanoparticles with more volatile SO2Cl2. SEM images of the composite membranes show that SSA nanoparticles are dispersed within the membranes uniformly, indicating the good organic compatibility of SSA particles. TEM images show that the composite membranes have improved ionic clusters distribution. The water uptakes of the composite membranes in water and under low relative humidities are all higher than that of the pristine SPEEK membrane. The addition of SSA enhances the conductivity obviously. The composite membrane containing 5wt.% SSA exhibits the highest conductivity of 0.13 Scm−1 at 80 °C, approximately 18.6% higher than that of the pristine SPEEK membrane and 8.6% higher than that of Nafion117. The composite membranes also show good thermal stability. These results imply the potential application of the SPEEK/SSA composite membranes as improved PEMs in PEMFC.Highlights▶ Silica sulfuric acid (SSA) nanoparticles were synthesized with SO2Cl2 and SiO2. ▶ SPEEK membranes doped with various contents of SSA particles were prepared. ▶ SSA particles have much improved organic compatibility compared with SiO2. ▶ SSA enhanced both the water uptake and conductivity of the membranes. ▶ The composite membrane with 5wt.% SSA shows the highest conductivity.
Co-reporter:Xiaoming Yan, Gaohong He, Shuang Gu, Xuemei Wu, Liguang Du, Yongdong Wang
International Journal of Hydrogen Energy 2012 Volume 37(Issue 6) pp:5216-5224
Publication Date(Web):March 2012
DOI:10.1016/j.ijhydene.2011.12.069
A series of imidazolium-functionalized polysulfones were successfully synthesized by chloromethylation-Menshutkin two-step method. PSf-ImOHs show the desired selective solubility: insoluble in alcohols (e.g., methanol and ethanol), and soluble in 50 vol.% aqueous solutions of acetone or tetrahydrofuran, implying their potential applications for both the alcohol-resistant membranes themselves and the ionomer solutions in low-boiling-point water-soluble solvents. PSf-ImOH also possesses very high thermal stability (TOD: 258 °C), higher than quaternary ammonium and quaternary phosphonium functionalized polysulfones (TOD: 120 °C and 186 °C, repsectively). Ion exchange capacity (IEC) of PSf-ImOH membranes ranges from 0.78 to 2.19 mmol g−1 with degree of chloromethylation from 42% to 132% of original chloromethylated polysulfone. As expected, water uptake, swelling ratio, and hydroxide conductivity increase with IEC and temperatures. With 2.19 mmol g−1 of IEC, the PSf-ImOH 132% membrane exhibits the highest hydroxide conductivity (53 mS cm−1 at 20 °C), higher than those of all other reported polysulfone-based HEMs (1.6–45 mS cm−1) and other imidazolium-functionalized HEMs (19.6–38.8 mS cm−1). In addition, PSf-ImOH membranes have low methanol permeability of 0.8–4.7 × 10−7 cm2 s−1, one order of magnitude smaller than that of Nafion212 membrane. All these properties indicate imidazolium-functionalized polysulfone is very promising for potential applications in alkaline membrane direct alcohol fuel cells.Highlights► An imidazolium-functionalized polysulfone was successfully synthesized. ► PSf-ImOHs show good solubility in low-boiling-point solvents. ► PSf-ImOH membranes have excellent alcohol tolerance and low methanol permeability. ► PSf-ImOH membrane exhibits high hydroxide conductivity and thermal stability.
Co-reporter:Xiangcun Li, Wu Xiao, Gaohong He, Wenji Zheng, Naisen Yu, Ming Tan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2012 Volume 408() pp:79-86
Publication Date(Web):20 August 2012
DOI:10.1016/j.colsurfa.2012.05.034
Dioctylsulfosuccinate sodium surfactant (AOT) was selected as a structure-directing agent to prepare mesoporous MgO adsorbent by a hydrothermal method. The anionic AOT surfactant combines with Mg(OH)2 crystallites to form AOT·Mg(OH)2 micelle colloids by hydrogen bonding and electrostatic attraction to template the mesopores with diameter of 10–20 nm in MgO nanoplates The whole process is composed of three stages: nucleation, orientation growth, and porecreating. The results demonstrated that the presence of AOT surfactant was essential to produce the mesopores and to adjust the structural parameters of the nanoplates. Because of their higher specific surface area and porous structure, the MgO materials exhibit a satisfactory adsorptive property to three typical azo dye pollutants, Congo red (471–588 mg/g), Methyl orange (∼370 mg/g) and Sudan III (∼180 mg/g), and good performance for decolorization of low-concentration dyes. The highly adsorption capacities of the adsorbents are ascribed to their mesoporous structures which can provide more interaction sites, facilitate the mass diffusion in pores and help the dye molecules to contact the adsorptive sites more easily. The present work provided an alternative approach for preparation of inorganic adsorbent with controlled porous structures and high adsorption ability for hazardous dyes.Graphical abstractNovel mesoporous MgO nanostructures: higher adsorption capacity and good decolorization performance to azo dye pollutants.Highlights► A novel mesoporous MgO adsorbent with higher surface area was prepared. ► The mechanism for designing the porous structures in MgO was proposed. ► The MgO materials exhibit high adsorption capability to azo dyes. ► The MgO show good performance for decolorization of low concentration dyes. ► The ability to obtain such MgO structure is useful in other adsorbent preparation.
Co-reporter:Chunxu Dong, Gaohong He, Hao Li, Rui Zhao, Yue Han, Yulin Deng
Journal of Membrane Science 2012 s 387–388() pp: 40-47
Publication Date(Web):
DOI:10.1016/j.memsci.2011.10.007
Co-reporter:Danmin Xing, Gaohong He, Zhongjun Hou, Pingwen Ming, Shufan Song
International Journal of Hydrogen Energy 2011 Volume 36(Issue 3) pp:2177-2183
Publication Date(Web):February 2011
DOI:10.1016/j.ijhydene.2010.11.022
Organically modified montmorillonites are valuable materials that have been used to improve the permeability, water retention, and proton conductivity of proton exchange membrane for fuel cells. A sulfonated montmorillonite/sulfonated poly (biphenyl ether sulfone)/Polytetrafluoroethylene (SMMT/SPSU-BP/PTFE) composite membrane was prepared for fuel cells. The thermal stability of the SMMT was tested by the thermogravimetry-mass spectrometry (TGA-MS) and its structure in the composite membrane was characterized by X-ray diffraction (XRD). It was found that SMMT was stable up to 205 °C and the interlayer distance of the nanoclay expanded from 1.43 nm to 1.76 nm after the organic sulfonic modification. The SMMT was completely exfoliated in the composite membranes. The properties of ion-exchange capacity, water uptake, swelling ratio, proton conductivity, and mechanical strength of the composite membranes were investigated as well. The good water retention of SMMT made the SMMT/SPSU-BP and SMMT/SPSU-BP/PTFE composite membranes have about 20% more bound water than the SPSU-BP membrane. Due to the reinforce effect of the PTFE porous film, the SMMT/SPSU-BP/PTFE composite membrane presented low swelling even at elevated temperature and high stress strength. All of the properties indicate that the SMMT/SPSU-BP/PTFE composite membrane is very promising as the PEM for medium temperature PEMFCs.
Co-reporter:Yinhua Li, Jian Gong, Gaohong He, Yulin Deng
Synthetic Metals 2011 Volume 161(1–2) pp:56-61
Publication Date(Web):January 2011
DOI:10.1016/j.synthmet.2010.10.034
In this work, a new method for the synthesis of polyaniline (PANI) nanotubes was presented. Experimentally, Mn2O3 nanofibers prepared by electrospinning technique were used as the oxidant template to initiate the polymerization of aniline in acid solution. After reaction, polyaniline shells were formed on the Mn2O3 nanofiber surface, and the Mn2O3 nanofibers were spontaneously removed. As a result, PANI nanotubes were obtained. As-prepared PANI nanotubes show an average diameter of 80 nm and inner diameter of 38 nm. The final PANI nanotubes were characterized by SEM, EDX, TEM, FTIR and XRD. The gas sensing of as-obtained PANI nanotubes was also investigated. It was found that the PANI nanotube sensing device could detect as low as 25 ppb NH3 in air at room temperature with good reversibility.
Co-reporter:Yinhua Li, Jian Gong, Gaohong He, Yulin Deng
Materials Chemistry and Physics 2011 Volume 129(1–2) pp:477-482
Publication Date(Web):15 September 2011
DOI:10.1016/j.matchemphys.2011.04.045
Polyaniline/titanium dioxide (PANI/TiO2) composite nanofibers were prepared by combining the electrospinning technique with chemical oxidation polymerization. Firstly, Mn3O4/TiO2 nanofibers were prepared by electrospinning, and then the Mn3O4 in the Mn3O4/TiO2 nanofibers acted as an oxidant to oxidatively polymerize aniline. As a result, Mn3O4 was completely consumed while PANI/TiO2 composite nanofibers were formed. The gas sensors of the composite nanofibers with different PANI to TiO2 ratios were fabricated on home-made gold electrodes, and the sensing property for ammonia gas detection was investigated at room temperature. Results showed that the composite nanofiber sensor could detect as low as 25 ppb ammonia gas, which is superior to the PANI nanofiber without TiO2 nanoparticles. The sensing sensitivity of the composite nanofibers strongly depends on the ratio of PANI to TiO2. The mechanism of sensitivity enhancement of the PANI nanofiber sensors mixed with TiO2 nanoparticles was also discussed.Highlights► A simple method for preparation of polyaniline/TiO2 composite nanofibers using electrospun nanofibers of Mn3O4/TiO2 as the templates was reported in this study. ► The p–n junction between polyaniline and TiO2 surface could significantly enhance the sensitivity of the ammonia sensing. ► The sensor made from these composite nanofibers can detect 25 ppb ammonia in gas, which is much higher than that of pure polyaniline nanofibers.
Co-reporter:Xiaoming Yan, Gaohong He, Shuang Gu, Xuemei Wu, Liguang Du, Haiyan Zhang
Journal of Membrane Science 2011 375(1–2) pp: 204-211
Publication Date(Web):
DOI:10.1016/j.memsci.2011.03.046
Co-reporter:Xiangcun Li, Vijay T. John, Jingjing Zhan, Gaohong He, Jibao He, and Leonard Spinu
Langmuir 2011 Volume 27(Issue 10) pp:6252-6259
Publication Date(Web):April 18, 2011
DOI:10.1021/la105149p
Mesoporous SiO2/TiO2/Fe2O3 particles containing macropores of about 50 nm in diameter have been prepared by an aerosol process using cetyltrimethylammonium bromide (CTAB) as a templating agent. In contrast to the traditional templating effect of CTAB to form ordered mesoporous silicas, the morphology here is vastly different due to the presence of precursor iron salts. The particles have mesoporosity templated by CTAB but additionally have large voids leading to a combined macroporous and mesoporous structure. The morphology is explained through the formation of colloidal structures containing species such as CTA+X–1Fe3+ colloids in the aerosol droplets, indicating of a salt bridging effect. This dual porosity has applied implications, as the macropores provide easy entry to the particle interior in potentially diffusion limited situations. Furthermore, the particles encapsulate Fe2O3 and contain TiO2 leading to the dual functional properties of magnetic response and photocatalytic activity.
Co-reporter:Lingling Zhang, Gaohong He, Wei Zhao, Fei Nie, Xiangcun Li, Ming Tan
Journal of Membrane Science 2011 371(1–2) pp: 141-147
Publication Date(Web):
DOI:10.1016/j.memsci.2011.01.027
Co-reporter:Lingling Zhang, Gaohong He, Wei Zhao, Ming Tan, Xiangcun Li
Separation and Purification Technology 2010 Volume 73(Issue 2) pp:188-193
Publication Date(Web):18 June 2010
DOI:10.1016/j.seppur.2010.03.024
Asymmetric polyetherimide (PEI) membranes have been prepared by phase-inversion process from casting solution containing n-methyl-2-pyrrolidone as a solvent and formamide (FM) as an additive. The effects of FM concentration on the structure and gas separation performance of the PEI membranes have been investigated and analyzed in terms of the casting solution viscosity, phase diagram, and solubility parameter difference. With the increase of FM concentration, the casting solution becomes thermodynamically unstable and easier to cause casting solution demixing, but the precipitation rate decreases because of the increased casting solution viscosity. The experimental results reveal that the structure of the dense skin layer strongly depends on the content of FM in the casting solution, and the gas permeance of the PEI membrane is markedly improved by the addition of FM. After coated with silicone rubber, the membrane prepared from the casting solution with 28.0 wt.% of PEI and 3.0 wt.% of FM exhibits the H2 permeance of 24.6 GPU (1 GPU = 10−6 cm3/cm2 s cmHg), combining with the O2/N2 and H2/N2 separation factors of 7.0 and 153.0, respectively.
Co-reporter:Shuang Gu;Xuemei Wu;Zhengwen Hu;Leilei Wang;Gongkui Xiao ;Lin Peng
Journal of Applied Polymer Science 2010 Volume 116( Issue 2) pp:852-860
Publication Date(Web):
DOI:10.1002/app.31547
Abstract
Poly(vinylidene fluoride)/sulfonated poly(phthalazinone ether sulfone ketone) (PVdF/SPPESK) blend membranes are successfully prepared by solution blending method for novel proton exchange membrane (PEM). PVdF crystallinity, FTIR-ATR spectroscopy, thermal stability, morphology, water uptake, dimension stability, and proton conductivity are investigated on PVdF/SPPESK blends with different PVdF contents. XRD and DSC analysis reveal that the PVdF crystallinity in the blends depends on PVdF content. The FTIR-ATR spectra indicate that SPPESK remains proton-conducting function in the blends due to the intactness of SO3H group. Thermal analysis results show a very high thermal stability (Td1 = 246–261°C) of the blends. PVdF crystallinity and morphology study demonstrate that with lower PVdF content, PVdF are very compatible with SPPESK. Also, with lower PVdF content, PVdF/SPPESK blends possess high water uptake, e.g., P/S 10/90 and P/S 15/85 have water uptake of 135 and 99% at 95°C, respectively. The blend membranes also have good dimension stability because the swelling ratios are at a fairly low level (e.g., 8–22%, 80°C). PVdF/SPPESK blends with low PVdF content exhibit very high proton conductivity, e.g., at 80°C, P/S 15/85 and P/S 10/90 reach 2.6 × 10−2 and 3.6 × 10−2 S cm−1, respectively, which are close to or even higher than that (3.4 × 10−2 S cm−1) of Nafion115 under the same test condition. All above properties indicate that the PVdF/SPPESK blend membranes (particularly, with 10–20% of PVdF content) are very promising for use in PEM field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Wei Zhao, Gaohong He, Lingling Zhang, Jia Ju, Hong Dou, Fei Nie, Cuina Li, Hongjing Liu
Journal of Membrane Science 2010 350(1–2) pp: 279-285
Publication Date(Web):
DOI:10.1016/j.memsci.2010.01.002
Co-reporter:Xiangcun Li, Gaohong He, Wenji Zheng, Gongkui Xiao
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2010 360(1–3) pp: 150-158
Publication Date(Web):
DOI:10.1016/j.colsurfa.2010.02.026
Co-reporter:Xiangcun Li, Gaohong He, Gongkui Xiao, Hongjing Liu, Mei Wang
Journal of Colloid and Interface Science 2009 Volume 333(Issue 2) pp:465-473
Publication Date(Web):15 May 2009
DOI:10.1016/j.jcis.2009.02.029
ZnO nanostructures with different morphologies and optical properties were prepared by a simple microemulsion process, and PEG400 was used as a directing agent. The samples were characterized by TEM, XRD, FTIR, and TG-DTA analysis. The XRD spectra indicate that the ZnO crystal has a hexagonal wurtzite structure. Needle-like, columnar, and spherical ZnO samples were synthesized respectively with the increase of PEG400 concentration in Zn(NO3)2 solution. TEM images and thermogravimetric analysis reveal that the microemulsion interface and the PEG400 agent have a synergistic effect on the morphology and crystalline size transition of ZnO nanostructures. The optical properties of the samples were investigated by measuring the UV–Vis absorbance spectra at room temperature. All the samples exhibit strong UV absorption at around 365 nm. ZnO products with band gap energies at 3.06, 3.02, 2.95, and 2.85 eV were obtained with 0, 12.5, 25.0, and 50.0% of PEG400 in Zn(NO3)2 solution, respectively. The formation mechanism of the ZnO nanostructures was proposed and discussed in detail. The synergistic control of the microemulsion interface and the agent on the growth of crystal nuclei reported here provides an alternative approach for preparation of other well-defined nanostructures.Synthesis and morphology control of crystalline ZnO particles in microemulsions. Added PEG400 concentration (wt%), (a) 0.0%, (b) 12.5% or 25.0%, (c) 50.0%.
Co-reporter:Yuanfa Liu, Gaohong He, Xudong Liu, Gongkui Xiao, Baojun Li
Separation and Purification Technology 2009 Volume 67(Issue 1) pp:14-20
Publication Date(Web):18 May 2009
DOI:10.1016/j.seppur.2009.02.022
Computational fluid dynamics (CFD) simulations were carried out for fluid flow in baffle-filled membrane tubes, in which an array of central baffles or wall baffles was inserted. The commercial CFD package FLUENT, which employs the finite-volume method, was used for numerical computations. Through CFD simulations, the qualitative and quantitative properties of fluid dynamics in a baffle-filled channel can be obtained, which benefits to fully understand the effects of two types of baffles on flow pattern, behavior and feature. The simulation results show that the presence of baffles causes remarkable increases of the average velocity and shear stress on the tube wall, which can significantly improve the filtration performance. The flux enhancement is also attributed to the intense fluctuations of wall velocity and wall shear stress, which can greatly disrupt the development of boundary layer, as well as the growth of cake layer. The experimental results of crossflow microfiltration of calcium carbonate suspensions are consistent with the CFD simulations. However, the pressure drop along the baffle-filled membrane tube is significantly increased owing to the frequent changes in flow direction and the energy dissipation of turbulent flow.
Co-reporter:Shuang Gu, Gaohong He, Xuemei Wu, Yingjie Guo, Hongjing Liu, Lin Peng, Gongkui Xiao
Journal of Membrane Science 2008 Volume 312(1–2) pp:48-58
Publication Date(Web):1 April 2008
DOI:10.1016/j.memsci.2007.12.053
In order to further overcome the trade-off between high conductivity and good mechanical property of proton exchange membrane (PEM), direct covalent crosslinking of sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) and poly(vinyl alcohol) (PVA) was prepared through post-heating process. Polymer PVA has attractive advantages to be a crosslinker with SPPESK, since the crosslinking of SPPESK with PVA requires relatively lower crosslinking temperature and has much higher stability in water, compared with small molecule crosslinker of glycol and glycerol. The crosslinking is confirmed by solubility change and analysis of ion exchange capacity (IEC) and sulfur content (CS) of uncrosslinked and crosslinked SPPESK with PVA (Un S-P and Cr S-P). Calculation of degree of crosslinking (DC) of sulfonic group shows that most –SO3Hs of SPPESK are not involved in the crosslinking, which can maintain the ion exchange and proton transport function. ATR-FTIR spectra analysis manifests the PVA in Cr S-P are oxidized and dehydrated during the crosslinking process with SPPESK. Cr S-P membrane still has higher thermal stability, despite Td (252–273 °C) is less than that (306 °C) of pristine SPPESK. SEM images and XRD patterns show that the Cr S-P is a homogenous and amorphous material. Water uptake of Cr S-P membrane decreases with increasing PVA content, and Cr S-P membrane with lower PVA content (e.g. 15% and 20%) has high water uptake (111.1% and 98.0%) at 80 °C. All the swelling ratio values of Cr S-P (15–35% of PVA content) are at a lower level (≤36%) even at 80 °C. Some Cr S-P membranes (with lower PVA content) have much higher conductivity than that of stable pristine SPPESK, e.g. conductivity of S-P 85/15 reaches 2.00 × 10−2 S cm−1 which is almost twice as that (1.03 × 10−2 S cm−1) of SPPESK DS 81% membrane. All above properties of Cr S-P membrane (especially PVA content: 15–20%) indicate the kind of crosslinked sulfonated polymer with PVA is another alternative or prospective approach to prepare PEM.
Co-reporter:Chang Lin, Gaohong He, Chunxu Dong, Hongjing Liu, Gongkui Xiao and YuanFa Liu
Langmuir 2008 Volume 24(Issue 10) pp:5291-5298
Publication Date(Web):April 24, 2008
DOI:10.1021/la704079s
Recently, there has been an increasing interest in the breakage of water-in-oil (W/O) emulsions by the freeze/thaw method. Most of the previous works focused on the phase transition of the water droplet phase. This paper emphasizes the effect of continuous oil phase transition. A series of oils with different freezing points were used as oil phases to produce model emulsions, which were then frozen and thawed. The emulsion whose oil phase froze before the water droplet phase did (OFBW) on cooling was readily demulsified with a dewatering ratio as high as over 80%, but the emulsion whose oil phase did not freeze when the water droplet phase did (NOFBW) was relatively hard to break. The difference in demulsification performance between them resulted from the distinction between their demulsification mechanisms via the analyses of the emulsion stability, emulsion crystallization/melting behaviors, oil phase physical properties, and wettability of the frozen oil phase, etc. For the OFBW emulsion, the first-frozen oil phase was ruptured by the volume expansion of the subsequently frozen droplet phase, and meanwhile, some liquid droplet phase was drawn into the fine gaps/crevices of the frozen oil phase to bridge droplets, which were considered to be essential to the emulsion breakage, whereas for the NOFBW emulsion, the demulsification was attributed to the collision mechanism proposed in our previous work. The findings may provide some criteria for selecting a proper oil phase in the emulsion liquid membrane (ELM) process and then offer an alternative approach to recycle the oil phase for continuous operation. This work may also be useful for emulsion stability against temperature cycling.
Co-reporter:Chang Lin, Gaohong He, Xiangcun Li, Lin Peng, Chunxu Dong, Shuang Gu, Gongkui Xiao
Separation and Purification Technology 2007 Volume 56(Issue 2) pp:175-183
Publication Date(Web):15 August 2007
DOI:10.1016/j.seppur.2007.01.035
Freeze/thaw treatment has been widely investigated for phase separation of oil-in-water (O/W) emulsions. However, it is a new application for destroying the inverted emulsions, water-in-oil (W/O) emulsions. In this study, freeze/thaw treatment was used to break the W/O emulsions with loosely packed droplets that were produced from the oils generally adopted as membrane phase in emulsion liquid membrane (ELM) process. The effects of emulsion system parameters and freezing conditions on demulsification performance were investigated. A near linear relationship was observed between demulsification performance and water content (30–65%). Demulsification performance greatly increased with the increase of droplet size (2.7–7.3 μm), while it was slightly affected by oil type. Four freezing methods were employed including freezing in refrigerator, cryogenic bath, dry ice and liquid nitrogen. The best freezing method for water removal was freezing in cryogenic or dry ice, and its efficiency was over 70% for all experimental systems with 60% water content regardless of droplet size and oil phase type. Furthermore, microscopic process of demulsification was monitored using optical microscope and the coalescence of droplets was simulated. From the experiments, the gradual demulsification process induced by freeze/thaw was proven and a collision mechanism was proposed. Meanwhile, the volume expansion of water turning to ice and interfacial tension of oil–water interface were determined as main driving forces of demulsification. The proposed mechanism and driving forces can explain the influences of various parameters on demulsification performance well.
Co-reporter:Xuemei Wu;Shuang Gu;Wan Chen;Pingjing Yao;Xuemei Wu;Shuang Gu;Wan Chen;Pingjing Yao
Journal of Applied Polymer Science 2007 Volume 104(Issue 2) pp:1002-1009
Publication Date(Web):26 JAN 2007
DOI:10.1002/app.23819
A series of sulfonated PPESK (SPPESKs) were synthesized through a heterogeneous sulfonation process with fuming sulfuric acid as sulfonating agent in a chloroform solvent. Membranes prepared from SPPESKs were investigated and proved to be candidates of proton exchange membrane in fuel cell operating at high temperature and low humidity. The heterogeneous sulfonation reaction is verified to first occur on the interface of the acid phase and the chloroform phase, then went on in the acid phase. SPPESKs with sulfonation degree (DS) up to 2.0 are obtained through a new reprecipitation method. Effects of reaction temperature, reaction time, acid/polymer ratio, and chloroform/polymer ratio on the sulfonation reaction are reported in details. An increase in sulfonation degree results in the increase of hydrophilicity, bringing about a substantial gain in proton conductivity. SPPESK membranes exhibit high water uptake of about 105.4% with DS of 1.01, almost two times higher than that of Nafion® with similar dimensional variation. Conductivity values at 35°C, 60% R.H. ranging from 10−3 to 10−2 S/cm were measured, which are comparable to or higher than that of Nafion® 112 (1.635 × 10−2 S/cm) under the same test condition. Thermogravimetric analysis shows that SPPESK membranes are stable up to 290°C in N2. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1002–1009, 2007
Co-reporter:Shuang Gu, Gaohong He, Xuemei Wu, Chennan Li, Hongjing Liu, Chang Lin, Xiangcun Li
Journal of Membrane Science 2006 Volume 281(1–2) pp:121-129
Publication Date(Web):15 September 2006
DOI:10.1016/j.memsci.2006.03.021
Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) for proton exchange membranes were prepared by sulfonation of PPESK using fuming acid and sulfuric acid agent. The separation of SPPESK was carried out by precipitating in ether and then in acetone. The degree of sulfonation (DS) was determined by ion exchange or conductimetric titration method. The FTIR study and 1H NMR analysis were used to confirm the SPPESK has been synthesized successfully. Membranes were cast from SPPESK solution in NMP. Thermal stability, water uptake and swelling rate, proton conductivity and methanol permeability of SPPESK membranes were studied. SPPESK have excellent thermal stability (DS = 28–132%; Td: 300–305 °C; Tg: 287–301 °C), appropriate water uptake (≤ 78%) and swelling rate (≤ 37%) when DS ≤ 81%. The conductivity of SPPESK membranes increases with DS and temperature. The conductivity of SPPESK 81% and SPPESK 91% reach 1.3 and 3.0 × 10−2 S/cm at 80 °C, near to that of Nafion115 (3.1 × 10−2 S/cm) at the same conditions. The apparent activation energies of the conductivity ΔEa of membranes with SPPESK 81% and SPPESK 91% are 20.5 and 22.2 kJ/mol, respectively. Those values are higher than that of Nafion115 (10.8 kJ/mol). SPPESK membranes exhibit methanol permeability at 15 °C from 1.3 × 10−7 to 9.7 × 10−8 cm2/s depending on the DS from 0 to 99%, those values are reduced by a factor of 32–42 for that of Nafion115 membrane (4.2 × 10−6 cm2/s) at the same conditions. All the above properties of SPPESK (especially DS 60–80%) indicate this material is promising for possible use in proton exchange membrane fuel cells, especially in direct methanol fuel cells.
Co-reporter:Zhengwen Hu, Gaohong He, Yuanfa Liu, Chunxu Dong, Xuemei Wu, Wei Zhao
Applied Clay Science (May 2013) Volumes 75–76() pp:134-140
Publication Date(Web):May 2013
DOI:10.1016/j.clay.2013.03.004
Co-reporter:Bing-Yan HAN, Xu-Fen HOU, Rong-Chao XIANG, Ming-Bo YU, Ying LI, Ting-Ting PENG, Gao-Hong HE
Chinese Journal of Analytical Chemistry (January 2017) Volume 45(Issue 1) pp:23-27
Publication Date(Web):January 2017
DOI:10.1016/S1872-2040(16)60985-4
A turn-on fluorescence analysis method was established for detection of Pb2+ based on aggregation-induced emission. Glutathione-protected non-noble metal copper nanoclusters (Cu NCs@GSH) showed nearly no fluorescence. However, the fluorescence intensity of Cu NCs@GSH was remarkably improved in the presence of Pb2+ and showed bright orange fluorescence. A fluorescence method for detection of Pb2+ was established based on this principle. The fluorescence change of the Cu NCs@GSH solution showed a linear relationship with Pb2+ concentration within the range of 200–700 μM. The limit of detection was 106 μM (S/N = 3). This method is simple, rapid and highly selective, and can be used for the visual qualitative detection of Pb2+ under ultraviolet (UV) lamp.
Co-reporter:Chunxu Dong, Yan Dai, Shengtao Jiang, Gaohong He
Journal of Environmental Chemical Engineering (February 2017) Volume 5(Issue 1) pp:877-883
Publication Date(Web):1 February 2017
DOI:10.1016/j.jece.2017.01.006
•Nano-Mg(OH)2 were used as pore former to prepare UF membrane by phase inversion.•Nano-Mg(OH)2 as additive improved both the pure water flux and retention ratio.•Membranes with Mg(OH)2 as additive have less cracks than those with LiCl.•Nonsolvent-insoluble but hydrophilic nanoparticles could be effective additive.Porous polymeric membranes have been widely applied to various water treatment processes. Water flux and retention ratio, which usually counterbalance each other, are two critical factors to evaluate the separating performance of a porous membrane for filtration. In this study, Mg(OH)2 nanoplatelets, which cannot be dissolved in both the casting solution and coagulation bath, were employed as additive to prepare PVDF ultrafiltration membrane via phase inversion method induced by immersion precipitation. After the nanoplatelets (≤4 wt%) were completely removed from the Mg(OH)2/PVDF hybrid membrane by the dilute hydrochloric acid, it is exciting to find that both the water flux and retention ratio of final production membranes greatly increased, with a little decrease of mechanical strength. Compared with those membranes prepared with soluble LiCl, the membranes using Mg(OH)2 had a reduced possibility to the formation of cracks on membrane surface. This work suggests that nonsolvent-insoluble but hydrophilic nanoparticles have greatly potential application as additive in the filtration membrane preparation.
Co-reporter:Bo Chen, Xiaobin Jiang, Wu Xiao, Yanan Dong, Issam El Hamouti, Gaohong He
Journal of Natural Gas Science and Engineering (August 2016) Volume 34() pp:563-574
Publication Date(Web):1 August 2016
DOI:10.1016/j.jngse.2016.07.018
•Dual-membrane process is more efficient than single-membrane-based processes.•Dual-membrane process has higher separation performance when selectivities increase.•Dual-membrane process provides lower investment, operational and CO2 avoidance cost.•Membrane module configuration and separation sequence are influential.•Models for dual and single-membrane are developed in simulation platform.Membrane-based natural gas pretreatment process is able to efficiently recover hydrocarbons and separate low-cost CO2 for enhanced gas recovery (EGR). Dual-membrane module (DMM) is an enhanced module configuration for membrane gas separation, which synchronously recovering CO2 and hydrocarbons by housing CO2-selective and hydrocarbon-selective membranes in the same module. Implementing DMMs in natural gas pretreatment system could significantly improve the separation performance of membranes, and further reduce investment and operational costs; however, the impacts of separation sequence still require intensive investigations. In this work, two DMM-based processes are proposed and compared with conventional single-membrane-based processes, aiming to find the optimal separation sequence and quantify the enhancing effects of DMMs. The results indicate that condensation-DMM is the optimal process design, which is able to provide 90-mol%-purity CO2 for EGR, and reduce 3–12% investment cost and CO2 avoidance cost. The sensitivity analysis of membrane selectivity shows that, the DMM-based processes demands lower investment cost than single-membrane-based processes with elevated membrane selectivities, and the DMM-condensation becomes the best-performance process design. The effect implies that the synergetic enrichment effect inside DMMs could amplify the impacts of membrane selectivity, enabling the DMMs to provide higher separation performance. This work demonstrates the potential applications of DMMs, and indicates that employing DMM to natural gas industry is an effective solution for current-available and advanced membrane materials.
Co-reporter:Yuanfa LIU, Gaohong HE, Luhui DING, Hong DOU, Jia JU, Baojun LI
Chinese Journal of Chemical Engineering (August 2012) Volume 20(Issue 4) pp:617-624
Publication Date(Web):1 August 2012
DOI:10.1016/S1004-9541(11)60226-7
This paper reports experimental and computational fluid dynamics (CFD) studies on the performance of microfiltration enhanced by a helical screw insert. The experimental results show that the use of turbulence promoter can improve the permeate flux of membrane in the crossflow microfiltration of calcium carbonate suspension, and flux improvement efficiency is strongly influenced by operation conditions. The energy consumption analysis indicates that the enhanced membrane system is more energy saving at higher feed concentrations. To explore the intrinsic mechanism of flux enhancement by a helical screw insert, three-dimensional CFD simulation of fluid flow was implemented. It reveals that hydrodynamic characteristics of fluid flow inside the channel are entirely changed by the turbulence promoter. The rotational flow pattern increases the scouring effect on the tube wall, reducing the particle deposition on the membrane surface. The absence of stagnant regions and high wall shear stress are responsible for the enhanced filtration performance. No secondary flow is generated in the channel, owing to the streamline shape of helical screw insert, so that the enhanced performance is achieved at relatively low energy consumption.
Co-reporter:Xuehua Ruan, Gaohong He, Baojun Li, Xiaoming Yan, Yan Dai
Chemical Engineering Science (7 April 2014) Volume 107() pp:245-255
Publication Date(Web):7 April 2014
DOI:10.1016/j.ces.2013.11.046
•A thermodynamic model is proposed for mass transfer in gas membrane separation.•Chemical potential change is used to discern work loss in RMC and CMC frameworks.•The mix of local permeate differing in composition reduces efficiency seriously.•Membrane stages with lower efficiency are ascertained in retrofitting frameworks.•Efficiency is enhanced by partially retrofitting RMC with proper capital cost.Thermodynamic analysis can discern those energy requirements which might be decreased in the separation system. In this work a theoretical model based on nonequilibrium thermodynamics was established to analyze the free energy change and the key points governing separation efficiency in gas membrane separation. Mass transfer in membranes was treated to be a two-step process in the model: species selectively permeate across membrane to form a series of local permeate gases, then the local permeate gases converge into a bulk permeate stream. Thus the total work required by the membrane process was identified as (i) the work to drive mass permeation, (ii) the work wasted by permeate mixing, and (iii) the minimum separation work. The analysis of two typical systems – the recycle membrane cascade (RMC) and the continuous membrane column (CMC) – revealed that the work wasted by permeate mixing seriously affects the free energy efficiency. This work wastage can be reduced by retrofitting process frameworks. Subsequently, the analysis was used to identify the serious work-losing stages in the RMC. Finally, a partially retrofitted RMC was proposed with tangible reductions in both equipment investment and energy consumption.
Co-reporter:Lingling Zhang, Gaohong He, Wei Zhao, Ming Tan, Xiangcun Li
Separation and Purification Technology (18 June 2010) Volume 73(Issue 2) pp:188-193
Publication Date(Web):18 June 2010
DOI:10.1016/j.seppur.2010.03.024
Asymmetric polyetherimide (PEI) membranes have been prepared by phase-inversion process from casting solution containing n-methyl-2-pyrrolidone as a solvent and formamide (FM) as an additive. The effects of FM concentration on the structure and gas separation performance of the PEI membranes have been investigated and analyzed in terms of the casting solution viscosity, phase diagram, and solubility parameter difference. With the increase of FM concentration, the casting solution becomes thermodynamically unstable and easier to cause casting solution demixing, but the precipitation rate decreases because of the increased casting solution viscosity. The experimental results reveal that the structure of the dense skin layer strongly depends on the content of FM in the casting solution, and the gas permeance of the PEI membrane is markedly improved by the addition of FM. After coated with silicone rubber, the membrane prepared from the casting solution with 28.0 wt.% of PEI and 3.0 wt.% of FM exhibits the H2 permeance of 24.6 GPU (1 GPU = 10−6 cm3/cm2 s cmHg), combining with the O2/N2 and H2/N2 separation factors of 7.0 and 153.0, respectively.
Co-reporter:Xiaoming Yan, Shuang Gu, Gaohong He, Xuemei Wu, Jay Benziger
Journal of Power Sources (15 March 2014) Volume 250() pp:
Publication Date(Web):15 March 2014
DOI:10.1016/j.jpowsour.2013.10.140
•Imidazolium-functionalized poly(ether ether ketone) was successfully synthesized.•PEEK-ImOH HEMs exhibit improved dimensional stability.•PEEK-ImOH HEMs exhibit high hydroxide conductivity (e.g., 52 mS cm−1 at 20 °C).•PEEK-ImOH HEMs exhibit good mechanical property (e.g., 78 MPa of tensile strength).•The methanol/O2 fuel cell employing PEEK-ImOH shows high performance.A series of imidazolium-functionalized poly(ether ether ketone)s (PEEK-ImOHs) were successfully synthesized by a two-step chloromethylation–Menshutkin reaction followed by hydroxide exchange. PEEK-ImOH membranes with ion exchange capacity (IEC) ranging from 1.56 to 2.24 mmol g−1 were prepared by solution casting. PEEK-ImOHs show selective solubility in aqueous solutions of acetone and tetrahydrofuran, but are insoluble in lower alcohols. PEEK-ImOH membranes with IEC of 2.03 mmol g−1 have high hydroxide conductivity (52 mS cm−1 at 20 °C), acceptable water swelling ratio (51% at 60 °C), and great tensile strength (78 MPa), and surprising flexibility (elongation-to-break of 168%), and high thermal stability (Decomposition temperature: 193 °C). In addition, PEEK-ImOH membranes show low methanol permeability (1.3–6.9 × 10−7 cm2 s−1). PEEK-ImOH membrane was tested in methanol/O2 fuel cell as both the HEM and the ionomer impregnated into the catalyst layer; the open circuit voltage is 0.84 V and the peak power density is 31 mW cm−2.
Co-reporter:Chang Lin, Gaohong He, Xiangcun Li, Lin Peng, Chunxu Dong, Shuang Gu, Gongkui Xiao
Separation and Purification Technology (15 August 2007) Volume 56(Issue 2) pp:175-183
Publication Date(Web):15 August 2007
DOI:10.1016/j.seppur.2007.01.035
Freeze/thaw treatment has been widely investigated for phase separation of oil-in-water (O/W) emulsions. However, it is a new application for destroying the inverted emulsions, water-in-oil (W/O) emulsions. In this study, freeze/thaw treatment was used to break the W/O emulsions with loosely packed droplets that were produced from the oils generally adopted as membrane phase in emulsion liquid membrane (ELM) process. The effects of emulsion system parameters and freezing conditions on demulsification performance were investigated. A near linear relationship was observed between demulsification performance and water content (30–65%). Demulsification performance greatly increased with the increase of droplet size (2.7–7.3 μm), while it was slightly affected by oil type. Four freezing methods were employed including freezing in refrigerator, cryogenic bath, dry ice and liquid nitrogen. The best freezing method for water removal was freezing in cryogenic or dry ice, and its efficiency was over 70% for all experimental systems with 60% water content regardless of droplet size and oil phase type. Furthermore, microscopic process of demulsification was monitored using optical microscope and the coalescence of droplets was simulated. From the experiments, the gradual demulsification process induced by freeze/thaw was proven and a collision mechanism was proposed. Meanwhile, the volume expansion of water turning to ice and interfacial tension of oil–water interface were determined as main driving forces of demulsification. The proposed mechanism and driving forces can explain the influences of various parameters on demulsification performance well.
Co-reporter:Junjiang Bao, Yan Lin, Ruixiang Zhang, Ning Zhang, Gaohong He
Energy Conversion and Management (1 July 2017) Volume 143() pp:312-325
Publication Date(Web):1 July 2017
DOI:10.1016/j.enconman.2017.04.018
•A two-stage condensation Rankine cycle (TCRC) system is proposed.•Net power output and thermal efficiency increases by 45.27% and 42.91%.•The effects of the condensation temperatures are analyzed.•14 working fluids (such as propane, butane etc.) are compared.For the low efficiency of the traditional power generation system with liquefied natural gas (LNG) cold energy utilization, by improving the heat transfer characteristic between the working fluid and LNG, this paper has proposed a two-stage condensation Rankine cycle (TCRC) system. Using propane as working fluid, compared with the combined cycle in the conventional LNG cold energy power generation method, the net power output, thermal efficiency and exergy efficiency of the TCRC system are respectively increased by 45.27%, 42.91% and 52.31%. Meanwhile, the effects of the first-stage and second-stage condensation temperature and LNG vaporization pressure on the performance and cost index of the TCRC system (net power output, thermal efficiency, exergy efficiency and UA) are analyzed. Finally, using the net power output as the objective function, with 14 organic fluids (such as propane, butane etc.) as working fluids, the first-stage and second-stage condensation temperature at different LNG vaporization pressures are optimized. The results show that there exists a first-stage and second-stage condensation temperature making the performance of the TCRC system optimal. When LNG vaporization pressure is supercritical pressure, R116 has the best economy among all the investigated working fluids, and while R150 and R23 are better when the vaporization pressure of LNG is subcritical.
Co-reporter:Xuemei Wu, Gaohong He, Shuang Gu, Zhengwen Hu, Xiaoming Yan
Chemical Engineering Journal (1 February 2010) Volume 156(Issue 3) pp:578-581
Publication Date(Web):1 February 2010
DOI:10.1016/j.cej.2009.04.033
The different states of water in a series of SPPESK membranes, including sulfonated poly (phthalazinone ether sulfone ketone) (SPPESK) membrane, cross-linked (XL) SPPESK membrane and SPPESK/polyacrylic acid (PAA) semi-interpenetrating polymer network (sIPN) membrane were investigated by low temperature differential scanning calorimetry (DSC) measurements. Only one melting peak was observed for each DSC curve, therefore the free water cannot be distinguished from freezing bound water in the experimental condition. The melting temperature of the freezable water was found to decrease when the content of the freezable water reduced. The content of non-freezing bound water decreased with the increase in total water uptake in each type of the membranes. It indicates that the total water uptake cannot exactly reveal the ability of tight water retention of the membranes. As compared with SPPESK/PAA membrane, SPPESK and XL-SPPESK membranes presented a higher ability of water retention because of higher content of non-freezing bound water measured. A schematic structural model is given to explain the interrelation of distribution of ionic groups (hydrophilic groups) and structure of polymers to the content of non-freezing bound water.
Co-reporter:Yuanfa Liu, Gaohong He, Ming Tan, Fei Nie, Baojun Li
Desalination (1 April 2014) Volume 338() pp:57-64
Publication Date(Web):1 April 2014
DOI:10.1016/j.desal.2014.01.015
•MF operation conditions greatly affect the flux improvement efficiency (FIE).•FIE first increases and then decreases with increasing TMP or inlet velocity.•Feed concentration always has a positive effect on the FIE.•TMP has a more important impact on the FIE than inlet velocity or concentration.•Optimization of MF operation conditions depends on the feed concentration.In this study, an artificial neural network (ANN) model for the turbulence promoter-assisted crossflow microfiltration (CFMF) process was successfully established, in which the inlet velocity, transmembrane pressure (TMP) and feed concentration were taken as inputs, and the flux improvement efficiency (FIE) by turbulence promoter was taken as output. Using the trained ANN model, the FIE can be predicted under CFMF operation conditions that are not included in the training database. It reveals that the FIE first increases and then decreases with increasing either TMP or inlet velocity, and increases with increasing feed concentration. Among three input variables, TMP has the most important effect on the FIE. The optimization of MF operation conditions was largely dependent on the feed concentration. The high FIE can be obtained by exerting both high inlet velocity (> 0.7 m/s) and low TMP ( <30 kPa) at a relatively low feed concentration ( <1 g/L), and both high inlet velocity (> 0.7 m/s) and high TMP (> 70 kPa) at a relatively high feed concentration (> 8 g/L). This study provides a useful guide for the applications of turbulence promoter in CFMF processes.Download full-size image
Co-reporter:Ning Zhang, Yuechun Song, Xuehua Ruan, Xiaoming Yan, Zhao Liu, Zhuanglin Shen, Xuemei Wu and Gaohong He
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 35) pp:NaN24209-24209
Publication Date(Web):2016/07/05
DOI:10.1039/C6CP03012B
The relationship between the proton conductive channel and the hydrated proton structure is of significant importance for understanding the deformed hydrogen bonding network of the confined protons which matches the nanochannel. In general, the structure of hydrated protons in the nanochannel of the proton exchange membrane is affected by several factors. To investigate the independent effect of each factor, it is necessary to eliminate the interference of other factors. In this paper, a one-dimensional carbon nanotube decorated with fluorine was built to investigate the independent effects of nanoscale confinement and fluorination on the structural properties of hydrated protons in the nanochannel using classical molecular dynamics simulation. In order to characterize the structure of hydrated protons confined in the channel, the hydrogen bonding interaction between water and the hydrated protons has been studied according to suitable hydrogen bond criteria. The hydrogen bond criteria were proposed based on the radial distribution function, angle distribution and pair-potential energy distribution. It was found that fluorination leads to an ordered hydrogen bonding structure of the hydrated protons near the channel surface, and confinement weakens the formation of the bifurcated hydrogen bonds in the radial direction. Besides, fluorination lowers the free energy barrier of hydronium along the nanochannel, but slightly increases the barrier for water. This leads to disintegration of the sequential hydrogen bond network in the fluorinated CNTs with small size. In the fluorinated CNTs with large diameter, the lower degree of confinement produces a spiral-like sequential hydrogen bond network with few bifurcated hydrogen bonds in the central region. This structure might promote unidirectional proton transfer along the channel without random movement. This study provides the cooperative effect of confinement dimension and fluorination on the structure and hydrogen bonding of the slightly acidic water in the nanoscale channel.
Co-reporter:Wanting Chen, Mengmeng Hu, Haochen Wang, Xuemei Wu, Xue Gong, Xiaoming Yan, Dongxing Zhen and Gaohong He
Journal of Materials Chemistry A 2017 - vol. 5(Issue 29) pp:NaN15047-15047
Publication Date(Web):2017/06/01
DOI:10.1039/C7TA01218G
A novel alkaline group, hexamethylenetetramine (HMTA) with four tertiary amine groups and β-hydrogen-absent structure, has been employed as mono-quaternization reagent to prepare HMTA mono-quaternized polysulfone anion exchange membranes (PSF-QuOH AEMs). Analyzed by molecular dynamics simulations, mono-quaternized HMTA shows a superior aggregating ability by strong electrostatic interaction with hydroxide to suppress water swelling even at high IECs. In particular, the PSF-QuOH membrane with a high IEC of 2.23 mmol g−1 exhibits a low swelling ratio of 21% even at 60 °C. The resulting high concentration of cationic groups and the interactions between multiple hydrogen atoms in HMTA and hydroxide/water are helpful to induce the formation of the continuous and efficient hydrogen-bond networks, promoting ionic transport. High hydroxide conductivity of 35 mS cm−1 is achieved at 20 °C. Excellent swelling resistance also benefits the mechanical and chemical stabilities of the PSF-QuOH membranes. A considerable mechanical strength of 17.7 MPa is observed in the fully hydrated membrane. The hydroxide conductivity is stable at around 86% of the initial value after 1 M KOH immersion at 60 °C for 168 h.
Co-reporter:Xuemei Wu, Wanting Chen, Xiaoming Yan, Gaohong He, Junjun Wang, Ying Zhang and Xiaoping Zhu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 31) pp:NaN12231-12231
Publication Date(Web):2014/05/01
DOI:10.1039/C4TA01397B
Poly(ether ether ketone) (PEEK) with multiple quaternary ammonium groups on pendent side chains is synthesized through the chloromethylation di-quaternization route, using bi-functional 1,4-diazabicyclo[2,2,2]octane (DABCO) as quaternization reagent. The materials are made into tough and transparent anion exchange membranes (AEMs) by solvent casting. The purpose is to promote efficient hydroxide ion conductive channels, which are particularly important and challenging to improve hydroxide conductivity of AEMs due to the inherently low mobility of hydroxide ions. Transmission electron microscopy (TEM) images show ionic clusters of bigger size scattering in the di-quaternized membranes compared with the mono-quaternized membranes. Given similar ion exchange capacities (IECs), the di-quaternized membranes exhibit much higher values of effective hydroxide ion mobility (∼3.5 × 10−4 cm2 s−1 V−1) than the mono-quaternized membranes (∼1.7 × 10−4 cm2 s−1 V−1). The structure of multiple quaternary ammonium groups on the pendent side chain promotes hydrophilic–hydrophobic micro-phase separation and efficient hydroxide ion conductive channels in the membranes. As a result, hydroxide conductivity of the di-quaternized membranes is about 2 to 3 fold higher than that of the mono-quaternized membranes with similar IEC, exhibiting a high value of about 35.3 mS cm−1 at 25 °C. At a certain IEC, the di-quaternized membranes have fewer pendent side chains on the polymer backbone, which also benefits the mechanical and chemical stabilities of the AEMs.
Co-reporter:Daishuang Zhang, Xiaoming Yan, Gaohong He, Le Zhang, Xinhong Liu, Fengxiang Zhang, Mengmeng Hu, Yan Dai and Sangshan Peng
Journal of Materials Chemistry A 2015 - vol. 3(Issue 33) pp:NaN16952-16952
Publication Date(Web):2015/06/22
DOI:10.1039/C5TA02913A
A novel integrally thin skinned asymmetric anion exchange membrane (ISAAEM) with sufficiently low ion exchange capacity (IEC) was proposed to improve the chemical stability of AEMs for vanadium flow batteries (VFBs). The ISAAEM with an IEC of 0.72 meq. g−1 showed low area resistance, slight VO2+ crossover and good electrochemical performance in VFBs.
![Poly[oxy[methyl(3,3,3-trifluoropropyl)silylene]]](http://img.cochemist.com/ccimg/25800/25791-89-3.png)
![Poly[oxy[methyl(3,3,3-trifluoropropyl)silylene]]](http://img.cochemist.com/ccimg/25800/25791-89-3_b.png)
![Poly[oxy(2,6-dimethyl-1,4-phenylene)]](http://img.cochemist.com/ccimg/25000/24938-67-8.png)
![Poly[oxy(2,6-dimethyl-1,4-phenylene)]](http://img.cochemist.com/ccimg/25000/24938-67-8_b.png)
![Tungstate(3-),tetracosa-m-oxododecaoxo[m12-[phosphato(3-)-kO:kO:kO:kO':kO':kO':kO'':kO'':kO'':kO''':kO''':kO''']]dodeca-,hydrogen (1:3)](http://img.cochemist.com/ccimg/1400/1343-93-7.png)
![Tungstate(3-),tetracosa-m-oxododecaoxo[m12-[phosphato(3-)-kO:kO:kO:kO':kO':kO':kO'':kO'':kO'':kO''':kO''':kO''']]dodeca-,hydrogen (1:3)](http://img.cochemist.com/ccimg/1400/1343-93-7_b.png)
