Co-reporter:Meiling Xiao;Jianbing Zhu;Ligang Feng;Changpeng Liu
Advanced Materials 2015 Volume 27( Issue 15) pp:2521-2527
Publication Date(Web):
DOI:10.1002/adma.201500262
Co-reporter:Jianbing Zhu, Meiling Xiao, Changpeng Liu, Junjie Ge, Jean St-Pierre and Wei Xing
Journal of Materials Chemistry A 2015 vol. 3(Issue 43) pp:21451-21459
Publication Date(Web):09 Sep 2015
DOI:10.1039/C5TA06181D
Non-platinum (NP) electrocatalysts with high activity and durability for oxygen reduction reactions (ORR) are required for fuel cells and other renewable systems. To avoid trial-and-error methods and achieve the rational design and synthesis of efficient NP catalysts, in-depth knowledge of the formation/growth mechanism of nanocatalysts and the origin of active sites is highly desirable. Here, we report a new class of NP catalysts with a novel structure of Fe3C encapsulated in N-doped carbon nanotubes/C. We study the formation mechanism of the nanostructure to pave the way for controlled fabrication of high-performance NP catalysts. The encapsulation of iron into carbon occurs during the first step of CNT growth and the surface functional groups on carbon black are identified as being essential for forming CNTs. The catalyst shows ultrahigh catalytic performance in both acid and alkaline media. We also examine the structure–performance dependency. The catalytic performance is highly dependent on the nanostructure and the encapsulation of Fe3C. Fe affects the catalytic performance through electronic effects rather than by directly participating in the active sites. This result is confirmed by DFT calculations, which show an increase in the density of states and a reduction in the local work function, XPS studies, and electrochemical measurements. The likelihood of N participating in the active sites is low because the catalytic performance does not depend on pyridinic and graphitic N.
Co-reporter:Jianbing Zhu, Meiling Xiao, Kui Li, Changpeng Liu and Wei Xing
Chemical Communications 2015 vol. 51(Issue 15) pp:3215-3218
Publication Date(Web):13 Jan 2015
DOI:10.1039/C4CC09528F
A novel PtFe@Pt core–shell nanostructure with a PtFe bimetallic core and a nanodendrite Pt shell was fabricated through a facile aqueous reduction process. Without any capping agent and/or surfactant, a clean Pt surface can be obtained. The novel nanostrutured crystals show superior electrocatalytic performance towards methanol oxidation due to the enlarged Pt surface area and the modified electronic structure of Pt.
Co-reporter:Jianbing Zhu, Meiling Xiao, Xiao Zhao, Changpeng Liu, Wei Xing
Journal of Power Sources 2015 Volume 292() pp:78-86
Publication Date(Web):1 October 2015
DOI:10.1016/j.jpowsour.2015.05.041
•TiO2@NCX was synthesized by pyrolysising polypyrrole and TiO2 composite.•Pt/TiO2@NCX catalysts exhibit high activity and stability towards MOR.•The high activity in MOR was due to the bifunctional mechanism and electronic effect.The development of advanced catalyst supports is a promising route to obtain active and durable electrocatalysts for methanol electro-oxidation reaction. In the current work, nitrogen-doped carbon encapsulated titanium dioxide composite (TiO2@NCX) is constructed and serves as support material for the Pt catalyst. The TiO2@NCX support is fabricated by the procedure of an in-situ polymerization and subsequent pyrolysis. The synthesized Pt/TiO2@NCX catalysts show enhanced electrocatalytic performance towards methanol electro-oxidation compared with the commercial Pt/C catalyst. The enhancement can be ascribed to combinatory effect of N-doped carbon and TiO2, in which the tolerance to CO-poisoning and the intrinsic kinetics of methanol oxidation reaction are simultaneously improved by the bifunctional mechanism and the electronic effect. As a result, the as-developed TiO2@NCX composite is a promising catalyst support material for the application in fuel cell.
Co-reporter:Meiling Xiao, Jianbing Zhu, Junjie Ge, Changpeng Liu, Wei Xing
Journal of Power Sources 2015 Volume 281() pp:34-43
Publication Date(Web):1 May 2015
DOI:10.1016/j.jpowsour.2015.01.169
•The oxidized states of CNTs were controlled by varied amounts of KMnO4 with a Hummer's method.•Pt/MO-CNTs showed the best performance towards MOR.•The Pt/MO-CNTs catalyst exhibited good activity and stability in single cell test.•The enhancement was due to the small metal size and the modified electron structure.Carbon nanotubes (CNTs) with different oxidation degrees are synthesized by the modified Hummer's method and used as the support materials for platinum (Pt) catalysts. The effect of their oxidation degree on the catalytic activity and stability of the supported Pt catalysts for methanol electrooxidation is investigated for the first time. The electrocatalytic activity for methanol oxidation reaction increases with increasing the oxidation degree due to more oxygen-containing species introduced to CNTs, which improves the dispersion of Pt nanoparticles and also modifies the electronic structure of Pt catalysts. However, under more severe oxidation condition, the stability of Pt catalysts decreases due to the destruction of graphitic structure of CNTs. Therefore, the optimized treatment condition for the CNTs is mild oxidation, which provides the supported Pt catalysts with both excellent catalytic activity and stability.
Co-reporter:Yang Hu, Jianbin Zhu, Qing Lv, Changpeng Liu, Qingfeng Li, Wei Xing
Electrochimica Acta 2015 Volume 155() pp:335-340
Publication Date(Web):10 February 2015
DOI:10.1016/j.electacta.2014.12.163
Cost-effective, active and stable electrocatalysts for the oxygen reduction reaction (ORR) are highly desirable for the wide-spread adoption of technologies such as fuel cells and metal-air batteries. Among the already reported non-precious metal catalysts, carbon-supported transition metal-nitrogen complexes, i.e., M-N/C catalysts, are the most promising candidate. Herein, by comparing the ORR activities of standard Fe-N/C catalysts synthesized with or without the doped phosphorus species, the promotional effect of phosphorus doping is discerned. Such phosphorus doping is achieved by using an acidic phosphate ester as a dopant in the synthesis, which introduces no change in catalyst morphologies and structures. The linked structure of phosphate ester cations with the nitrogen precursor, i.e., polyaniline chain, is favored for the evenly P doping of the catalyst, showing to a superior ORR activity to that for the undoped Fe-N/C catalyst. The activity and durability of the catalysts are demonstrated in direct methanol fuel cells.
Co-reporter:Wei Liu, Weiwei Cai, Changpeng Liu, Shimei Sun, Wei Xing
Fuel 2015 Volume 139() pp:308-313
Publication Date(Web):1 January 2015
DOI:10.1016/j.fuel.2014.08.066
•The removal of CO2 bubbles is promoted in the magnet integrated DMFC.•The promotion of CO2 removal can subsequently enhance the catalyst utilization.•A 12.5% enhancement in maximum power density by combining the magnetic field.A novel approach was proposed to promote CO2 removal from the anode catalyst layer of a liquid-fed passive direct methanol fuel cell (DMFC) by introducing Lorentz force via magnetic field integrating. Due to the promoted removal of CO2 micro-bubble, the physical block of triple-phase boundary in the anode catalyst layer was reduced evidently. CO2 removal was promoted through introducing forced convection around the CO2 bubbles which can be proved by the mathematical calculations. Performance of the vapor-fed DMFC, in where no CO2 bubble existing in the anode, did not change by the magnetic field, also indicated that the enhanced performance of the liquid-fed magnetic-coupled DMFC was resulted from the promotional CO2 removal. A 12.5% enhancement in maximum power density was obtained for the liquid-fed DMFC by combining the magnetic field.
Co-reporter:Jianbing Zhu, Meiling Xiao, Xiao Zhao, Changpeng Liu, Junjie Ge, Wei Xing
Nano Energy 2015 Volume 13() pp:318-326
Publication Date(Web):April 2015
DOI:10.1016/j.nanoen.2015.03.002
•Strong coupled Pt nanotubes/nitrogen-doped graphene (Pt NTs/NG) is fabricated.•NG improves the distribution and utilization of Pt NTs.•Pt NTs/NG shows high activity and durability towards oxygen reduction reaction.•Strong interaction between Pt and NG enhances the activity and durability of Pt.Design and synthesis of oxygen reduction reaction (ORR) catalysts with both high activity and durability is a challenging task for the novel energy systems. Here we report a very promising ORR catalyst composed of strongly coupled platinum nanotubes and nitrogen-doped graphene (Pt NTs/NG), which was synthesized by in-situ galvanic replacement reaction. The newly developed catalyst shows ultrahigh activity and durability towards ORR in acidic medium. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy together with electrochemical analyses indicated that the greatly enhanced performance is due to the strong interaction between platinum and nitrogen-doped graphene support. This hybrid catalyst system is of great potential for application in proton exchange membrane fuel cell.
Co-reporter:Jianbing Zhu, Meiling Xiao, Xiao Zhao, Kui Li, Changpeng Liu and Wei Xing
Chemical Communications 2014 vol. 50(Issue 81) pp:12201-12203
Publication Date(Web):14 Aug 2014
DOI:10.1039/C4CC04887C
A novel nitrogen doped carbon–graphene support for a direct methanol fuel cell was synthesised via thermal decomposition of the graphene oxide–polypyrrole composite. The supported catalysts show considerable enhancement of activity and stability towards the methanol electro-oxidation reaction. Physical characterizations reveal that the enhanced performance was due to a uniform particle dispersion and modified electronic structure of platinum nanoparticles by the support.
Co-reporter:Yuwei Zhang, Zhiguang Zhang, Wei Chen, Changpeng Liu, Wei Xing, Suobo Zhang
Journal of Power Sources 2014 Volume 258() pp:5-8
Publication Date(Web):15 July 2014
DOI:10.1016/j.jpowsour.2014.01.016
•Proton resistance increased due to phase separation at different polymer interface.•Phase separation is adverse to proton transfer process between different polymers.•Continuous distribution of polymer is needed for good proton conduction.The proton conductivity at the interface of Nafion and sulfonated polypyrrolone composite membrane decreases by 56% from 0.039 S cm−1 to 0.017 S cm−1, due to phase separation after annealing this binary composite membrane at 140 °C, which is 10 °C above the glass transition temperature of Nafion polymer. After annealing the membrane, the change in the relative intensity of the lower angles of the X-ray diffraction (XRD) peaks located at ca. 11.9°, 17.5° and 19.7° indicates an increase of the low spacing region for the polymer chains of the composite membrane and atomic force microscopy (AFM) measurement depicts a morphological evolution from an uniform dispersion to a spherules micro-structure, implying the aggregation of polymer chains of the annealed composite membrane. These results are combined to reveal there is a microphase separation of this binary composite membrane as it is annealed at 140 °C.
Co-reporter:Jianbing Zhu, Xiao Zhao, Meiling Xiao, Liang Liang, Changpeng Liu, Jianhui Liao, Wei Xing
Carbon 2014 Volume 72() pp:114-124
Publication Date(Web):June 2014
DOI:10.1016/j.carbon.2014.01.062
The exploration of advanced catalyst supports is a promising route to obtain electrocatalysts with high activity and durability. Herein, the nitrogen-doped graphitized carbon/TiO2 composite was fabricated and explored as support for the Pt catalyst. The composite support was constructed by carbonization of polypyrrole/TiO2 using cobalt nitrate and nickel nitrate as graphitizing catalysts. The resulting catalyst shows enhanced electrocatalytic performance for methanol electrooxidation compared with the commercial Pt/C catalyst. The enhancement can be ascribed to combinatory effect of N-doped graphitized carbon and TiO2, in which the tolerance to CO-poisoning and the intrinsic kinetics of methanol oxidation reaction were simultaneously improved by the bifunctional effect and the modification of the electronic structure. As a result, the as-developed nitrogen-doped graphitized carbon/TiO2 composite present attractive advantages for the application in fuel cell electrocatalyst.
Co-reporter:Jing Yang, Bin Wang, Yingfang Liu, Kunqi Wang, Wei Xing, Changpeng Liu
Journal of Power Sources 2014 Volume 248() pp:660-667
Publication Date(Web):15 February 2014
DOI:10.1016/j.jpowsour.2013.08.030
•A calculation is used to analyze series of porphyrins as sensitizers.•Photoelectrochemical biofuel cells were fabricated with the above porphyrins.•The haematoporphyrin showed the best performance of the series of porphyrins.•The theoretical calculation was consistent with the experimental results.Extending excited-state of sensitizer that absorbs visible photon and produces charge separation is of importance for a photoelectrochemical biofuel cell (PEBFC). In the present work, the dependence of series of porphyrins functionalized at β-positions as sensitizers' structures on their excited-state are analyzed with the density functional theory and time-dependent density functional theory. The calculated results expect that the radiative lifetime decreases in the order of haematoporphyrin > protoporphyrin IX > H2-mesoporphyrin IX. The designed PEBFCs with the above porphyrins as sensitizers are assembled, in which the photocurrent action spectra testifies that the order of the radiative lifetime is consistent with that of the incident photon-to-collected electron conversion efficiency (IPCE) value based on the series of porphyrins. All the experimental characteristics show that the porphyrin with ethanol group (–CHOH–CH3) at β-positions can enhance the photovoltaic performance of the PEBFC as expected.
Co-reporter:Yao Xiao, Qing Lv, Jianbing Zhu, Shikui Yao, Changpeng Liu and Wei Xing
RSC Advances 2014 vol. 4(Issue 41) pp:21176-21179
Publication Date(Web):23 Apr 2014
DOI:10.1039/C4RA02568G
Pt hollow nanotubes (Pt HNTs) with adjustable diameters as methanol oxidation electrocatalysts were synthesized through a galvanic replacement method, in which Ag nanowires with variable diameters obtained under controllable microwave irradiation conditions were used as the sacrificial templates. The Pt HNTs with a diameter of 100 nm (Pt-100) exhibited the highest catalytic activity, which was 1.6 times the state-of-the-art commercial Pt black, showing the advantage of hollow tube nanostructure over nanoparticle structure in electrocatalysis for the methanol oxidation reaction (MOR). Dependence of electrocatalytic activity on Pt HNT diameter reflects the Pt utilization effect in the geometrical view.
Co-reporter:Fengzhan Si, Junjie Ge, Chenyang Li, Liang Liang, Changpeng Liu, Wei Xing
International Journal of Hydrogen Energy 2014 Volume 39(Issue 6) pp:2489-2496
Publication Date(Web):14 February 2014
DOI:10.1016/j.ijhydene.2013.11.108
•Pt modified Pd/C catalysts controlled with haloids in a one-pot process.•Controllability of Pt on Pd surface was proved with physical tests.•Pt modified Pd/C controlled with Cl− has best HCOOH electrooxidation stability.Pt modified Pd/C catalysts were synthesized through galvanic replacement method in a one-pot synthetic process, where the replacement reaction was influenced greatly by the presence of the haloids (Cl− or Br−) in the solution. The catalysts with and without Pt modification were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-Ray spectroscopy (EDX) and electrochemical tests. The modified state and atomic ratio of Pt to Pd due to the variation of synthetic conditions were confirmed by the physical characterizations. The variation in structure/surface composition of the Pt–Pd/C catalysts leaded to different reaction mechanism and varied the performance of formic acid electrooxidation, which were confirmed by the electrochemical tests. The Pd/C catalyst modified with Pt in the presence of Cl− possesses satisfactory comprehensive performance, i.e. both stability and activity, for formic acid electrooxidation (FAEO). The results are of significance for designing catalysts for practical application of direct formic acid fuel cell and understanding mechanism of FAEO on noble metals composite structures.
Co-reporter:Jinfa Chang;Dr. Ligang Feng;Dr. Changpeng Liu;Dr. Wei Xing;Dr. Xile Hu
Angewandte Chemie International Edition 2014 Volume 53( Issue 1) pp:122-126
Publication Date(Web):
DOI:10.1002/anie.201308620
Abstract
The direct formic acid fuel cell is an emerging energy conversion device for which palladium is considered as the state-of-the-art anode catalyst. In this communication, we show that the activity and stability of palladium for formic acid oxidation can be significantly enhanced using nickel phosphide (Ni2P) nanoparticles as a cocatalyst. X-ray photoelectron spectroscopy (XPS) reveals a strong electronic interaction between Ni2P and Pd. A direct formic acid fuel cell incorporating the best Pd–Ni2P anode catalyst exhibits a power density of 550 mW cm−2, which is 3.5 times of that of an analogous device using a commercial Pd anode catalyst.
Co-reporter:Jinfa Chang;Dr. Ligang Feng;Dr. Changpeng Liu;Dr. Wei Xing;Dr. Xile Hu
Angewandte Chemie 2014 Volume 126( Issue 1) pp:126-130
Publication Date(Web):
DOI:10.1002/ange.201308620
Abstract
The direct formic acid fuel cell is an emerging energy conversion device for which palladium is considered as the state-of-the-art anode catalyst. In this communication, we show that the activity and stability of palladium for formic acid oxidation can be significantly enhanced using nickel phosphide (Ni2P) nanoparticles as a cocatalyst. X-ray photoelectron spectroscopy (XPS) reveals a strong electronic interaction between Ni2P and Pd. A direct formic acid fuel cell incorporating the best Pd–Ni2P anode catalyst exhibits a power density of 550 mW cm−2, which is 3.5 times of that of an analogous device using a commercial Pd anode catalyst.
Co-reporter:Meiling Xiao;Songtao Li;Xiao Zhao;Jianbing Zhu;Min Yin;Dr. Changpeng Liu;Dr. Wei Xing
ChemCatChem 2014 Volume 6( Issue 10) pp:2825-2831
Publication Date(Web):
DOI:10.1002/cctc.201402186
Abstract
Ultrathin PtCux (x=1, 2 and 3) nanowire networks (NWMs) with controllable compositions were successfully synthesized by using Triton X-100 as the structure-directing agent in aqueous solution. The as-prepared PtCux nanocrystals were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, and chronoamperometry. The results show that electrocatalytic performance of the PtCux NWNs towards the methanol oxidation reaction is enhanced relative to that of commercial Pt/C catalysts. Moreover, if the initial atomic ratio of Pt/Cu is 1:2, the corresponding PtCu2 NWNs catalyst generates mass activity that is 3.77-fold higher and specific activity that is 2.71-fold higher than the corresponding properties of commercial Pt/C catalysts. The enhanced activity can be attributed to a unique structure and a modified electronic effect.
Co-reporter:Meiling Xiao;Songtao Li;Jianbing Zhu;Kui Li;Dr. Changpeng Liu;Dr. Wei Xing
ChemPlusChem 2014 Volume 79( Issue 8) pp:1123-1128
Publication Date(Web):
DOI:10.1002/cplu.201402061
Abstract
The PtAu alloy nanowire networks (NWNs) were synthesized directly in an aqueous solution using Triton X-114 as the structure-inducing agent. The NMNs formed based on the oriented-attachment growth mechanism, and they exhibited dramatically enhanced electrocatalytic activity for formic acid electrooxidation compared with commercial Pt black. Besides the ensemble effect, the advantages of the unique structure, including superior electrical conductivity and faster electron-transfer for the electrochemical process, were regarded as the contributors to the superior catalytic activity of the as-prepared PtAu NWNs.
Co-reporter:Xiujuan Sun, Yuwei Zhang, Ping Song, Jing Pan, Lin Zhuang, Weilin Xu, and Wei Xing
ACS Catalysis 2013 Volume 3(Issue 8) pp:1726
Publication Date(Web):July 3, 2013
DOI:10.1021/cs400374k
For the goal of practical industrial development of fuel cells, inexpensive, sustainable, and high performance electrocatalysts for oxygen reduction reactions (ORR) are highly desirable alternatives to platinum (Pt) and other rare materials. In this work, sustainable fluorine (F)-doped carbon blacks (CB-F) as metal-free, low-cost, and high-performance electrocatalysts for ORR were synthesized for the first time. The performance (electrocatalytic activity, long-term operation stability, and tolerance to poisons) of the best one (BP-18F, based on Black Pearls 2000 (BP)) is on the same level as Pt-based or other best non-Pt-based catalysts in alkaline medium. The maximum power density of alkaline direct methanol fuel cell with BP-18F as the cathode (3 mg/cm2) is ∼15.56 mW/cm2 at 60 °C, compared with a maximum of 9.44 mW/cm2 for commercial Pt/C (3 mgPt/cm2). All these results unambiguously demonstrate that these sustainable CB-F catalysts are the most promising alternatives to Pt in an alkaline fuel cell. Since sustainable carbon blacks are 10 000 times less expensive and much more abundant than Pt or other rare materials, these CB-F electrocatalysts possess the best price/performance ratio for ORR to date.Keywords: energy; fluorine; fuel cell; metal-free electrocatalyst; oxygen reduction reaction
Co-reporter:Fengzhan Si, Jianhui Liao, Liang Liang, Changpeng Liu, Xinbo Zhang, Wei Xing
Journal of Power Sources 2013 Volume 225() pp:231-239
Publication Date(Web):1 March 2013
DOI:10.1016/j.jpowsour.2012.10.021
A series of Pt/C catalysts with controlled Pt particle sizes is synthesized using a surfactant-free process with ethylene glycol as the weak reducing agent. The Pt particle size can be regulated by controlling the pH of the Pt (IV) complex via the addition of different amounts of urea. The results of X-ray diffraction and transmission electron microscopy confirm that the Pt nanoparticles on the carbon exhibit good size controllability and dispersion. The electroactive surface area (ESA), the electron transfer coefficient, and the electrocatalytic activity to dimethyl ether electrooxidation are dependent on the Pt particle size, and a comparison of the electrochemical properties of the samples reveals that the relationships are parabolic. The results are important for understanding the mechanism of and designing an effective catalyst for dimethyl ether (DME) electrooxidation and providing a size-controlled synthetic method for Pt-based catalysts.Highlights► Pt/C catalysts with controlled Pt particle size were synthesized without surfactant. ► Ethylene glycol was employed as both solvent and reducing agent. ► Pt particle was regulated by changing the amount of added urea. ► Electrocatalysis of DME oxidation vs. Pt particle size exists a parabolic trend.
Co-reporter:Jinfa Chang, Xiujuan Sun, Ligang Feng, Wei Xing, Xiujuan Qin, Guangjie Shao
Journal of Power Sources 2013 Volume 239() pp:94-102
Publication Date(Web):1 October 2013
DOI:10.1016/j.jpowsour.2013.03.066
•Palladium nanoparticles supported on the N-doped carbon materials used for FAEO.•Pd/N-C-900 catalyst shows the best catalytic activity and stability for FAEO.•Syngenetic effect of catalyst and support proposed for the catalytic process.Nitrogen-doped acetylene carbon black (N-C) is prepared by annealing acetylene carbon black and melamine under the protection of N2 at different temperatures. The resultant N-C materials are used as the support of Pd catalyst (Pd/N-C) for formic acid electrooxidation (FAEO). The catalytic activity of the Pd/N-C catalyst towards FAEO is evaluated by cyclic voltammetry, COad stripping voltammetry and chronoamperometry. The results show that when the heat-treatment temperature of support is 900 °C, the corresponding catalyst, Pd/N-C-900, generate 2.84-fold and 0.96-fold higher activity than homemade and commercial Pd/C catalysts in 0.5 M H2SO4 and 0.5 M HCOOH solution. The COad stripping voltammetry results demonstrate that Pd/N-C-900 has much better resistance to CO poisoning. Moreover, the effect of formic acid concentration and the temperature on the Pd/N-C catalysts are also explored, which confirms the really enhanced performances for FAEO. It is founded that the doping of nitrogen results an increase in the performance for FAEO due to the improved Pd nanoparticles (Pd NPs) dispersion and the modified electronic effect. The results indicate that the Pd/N-C catalyst has great application prospect as a high-performance anode catalyst for direct formic acid fuel cells (DFAFCs).
Co-reporter:Jianhui Liao, Jingshuai Yang, Qingfeng Li, Lars N. Cleemann, Jens Oluf Jensen, Niels J. Bjerrum, Ronghuan He, Wei Xing
Journal of Power Sources 2013 Volume 238() pp:516-522
Publication Date(Web):15 September 2013
DOI:10.1016/j.jpowsour.2013.03.194
•Oxidative degradation of PBI membranes investigated under Fenton radical attacks.•Accelerating effect of ferrous ions on the polymer degradation confirmed.•Suppressing effect of phosphoric acid on the polymer degradation first reported.•Durability tests verified the positive effect of the acid under ferrous contamination.Phosphoric acid doped polybenzimidazole membranes have been explored as proton exchange membranes for high temperature polymer electrolyte membrane fuel cells. Long-term durability of the membrane is of critical concern and has been evaluated by accelerated degradation tests under Fenton conditions. In this study effects of phosphoric acid and ferrous ions were investigated by measurements of the weight loss, intrinsic viscosity and size exclusion chromatography (SEC) of the polymer membranes. Ferrous ions resulted in, as expected, catalytic formation of peroxide radicals and hence the accelerated polymer degradation in terms of weight loss and molecular weight decrease. The presence of phosphoric acid as an inevitable dopant of the membranes, on the other hand, significantly impeded the membrane degradation by means of metal ion complexing, decreased pH, and acid–base interactions with the amino groups of the polymer. Fuel cell durability tests with contaminations of ferrous ions did show considerable performance degradation, however, primarily due to the catalyst deterioration rather than the membrane degradation.
Co-reporter:Jing Yang, Ligang Feng, Fengzhan Si, Yuwei Zhang, Changpeng Liu, Wei Xing, Kunqi Wang
Journal of Power Sources 2013 Volume 222() pp:344-350
Publication Date(Web):15 January 2013
DOI:10.1016/j.jpowsour.2012.08.062
H2-mesoporphyrin IX and Zn-mesoporphyrin IX have been investigated as sensitizers for the titanium dioxide (TiO2) film electrode to construct a new two-compartment photoelectrochemical biofuel cell (PEBFC). The PEBFC can convert the light and chemical energy to electricity by consuming photons and oxidizing glucose. The two sensitizers are similar with two carboxyl anchoring groups, except that the central hydrogen atoms in the H2-mesoporphyrin IX are replaced by zinc. To determine how cell performance is affected by the sensitizer, we analyze the photochemical and photoelectrochemical properties of the two sensitizers by physical characterization and photoelectrochemical experiments. The UV–Vis absorption spectra and X-ray photoelectron spectra (XPS) indicate that the interactions between the sensitizer and TiO2 decrease in the order of H2-mesoporphyrin IX > Zn-mesoporphyrin IX. The interactions are also determined by Fourier transform infrared (FTIR) spectra which indicate that the two sensitizers are adsorbed on the TiO2 film through the carboxyl groups. The photovoltaic characteristics show the Zn-mesoporphyrin IX is less effective in comparison with the H2-mesoporphyrin IX, since the Zn-mesoporphyrin IX enhances the back electron-transfer process, producing lower IPCE and current. These results reveal that the H2-mesoporphyrin IX is a more efficient sensitizer compared with the Zn-mesoporphyrin IX for the PEBFC.Highlights► A new two-compartment photoelectrochemical biofuel cell is fabricated. ► This cell is based on H2-mesoporphyrin IX or Zn-mesoporphyrin IX sensitizer. ► H2-mesoporphyrin IX shows a better performance than Zn-mesoporphyrin IX.
Co-reporter:Yang Hu, Xiao Zhao, Yunjie Huang, Qingfeng Li, Niels J. Bjerrum, Changpeng Liu, Wei Xing
Journal of Power Sources 2013 Volume 225() pp:129-136
Publication Date(Web):1 March 2013
DOI:10.1016/j.jpowsour.2012.10.013
Non-precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) are an active subject of recent research on proton exchange membrane fuel cells. In this study, we report a new approach to preparation of self-supported and nano-structured NPMCs using pre-prepared polyaniline (PANI) nanofibers as both nitrogen and carbon precursors. The synthesized NPMCs possess nanoworm structures preserved from the PANI precursor and exhibit high onset potential of 0.905 V vs. RHE and selective activity of nearly four-electron ORR pathways. A significant enhancement in the intrinsic activity and onset potential for the ORR is observed when the Fe content in the precursor is increased from 0 to 3.0 wt.%, while further addition to 10.0 wt.% results in a decrease in the catalytic activity.Highlights► Novel preparation of self-supported and nano-structured NPMCs for ORR. ► An onset potential of 0.905 V vs. RHE and nearly four-electron ORR pathway. ► Effects of ferrous species in precursors on the final catalysts explored. ► Onset ORR potentials increasing with the initial Fe content from 0 to 3.0 wt.%.
Co-reporter:Yunjie Huang, Qingfeng Li, Tatiana V. Anfimova, Erik Christensen, Min Yin, Jens Oluf Jensen, Niels J. Bjerrum, Wei Xing
International Journal of Hydrogen Energy 2013 Volume 38(Issue 5) pp:2464-2470
Publication Date(Web):19 February 2013
DOI:10.1016/j.ijhydene.2012.11.125
Co-reporter:Weiwei Cai, Liang Liang, Yuwei Zhang, Wei Xing, Changpeng Liu
International Journal of Hydrogen Energy 2013 Volume 38(Issue 1) pp:212-218
Publication Date(Web):11 January 2013
DOI:10.1016/j.ijhydene.2012.09.155
We first experimentally verified the real contribution of formic acid (FA) in the direct formic acid fuel cell (DFAFC). By comparing the cell performance of the fuel cell fueled with FA and methanol, we found that FA not only acts as fuel in the fuel cell, but is also of benefit to proton conducting and triple phase boundary (TPB) building in the anode. Considering the real contribution and the special mass transfer behavior of FA in the fuel cell, the anode was reasonably designed and optimized. Carbon cloth was selected as the optimized anode diffusion layer to achieve quick methanol transfer from fuel reservoir to anode catalyst. The decal method was proved to be the better choice for membrane electrode assembly (MEA) fabrication than the traditional hot pressing because it can result in better TPB building and lowering the FA crossover. DFAFC performed approximately 60% better after these anodic micro structure optimizations.Highlights► Real contribution of formic acid (FA) in DFAFC was studied. ► FA was proved to be of great benefit to the proton conduction and TPB building. ► The anode of DFAFC was optimized with the guiding of FA's real contribution. ► Construction and fabrication method of MEA were adjusted. ► The passive DFAFC performed 60% better after structural optimizing.
Co-reporter:Xiao Zhao, Jianbing Zhu, Weiwei Cai, Meiling Xiao, Liang Liang, Changpeng Liu and Wei Xing
RSC Advances 2013 vol. 3(Issue 6) pp:1763-1767
Publication Date(Web):07 Dec 2012
DOI:10.1039/C2RA22536K
We demonstrate a self-sacrifice-templating method to synthesize Pt–Pb hollow-sphere networks, in which the hollow-spheres arise from the self-sacrifice of in situ formed Pb nanoclusters without the use of a pre-existing template and the networks originate from the diffusion-limited aggregation process. Of particular interest is that the as-prepared Pt–Pb catalyst shows a significantly enhanced activity for formic acid electrooxidation.
Co-reporter:Liang Yan, Jianhui Liao, Ligang Feng, Xiao Zhao, Liang Liang, Wei Xing, Changpeng Liu
Journal of Electroanalytical Chemistry 2013 Volume 688() pp:49-52
Publication Date(Web):1 January 2013
DOI:10.1016/j.jelechem.2012.09.010
A novel electrochemical methanol sensor was to be coupled with the direct methanol fuel cells (DMFC) to real-time monitor the used concentration of methanol solution. The sensor effectively operates on a basis of measuring the current output produced by methanol diffusion through the Nafion 115 membrane. The sensor displays a robust sensitivity to the widely used methanol concentration (from 0 to 5 M) and operating temperature (from 30 to 60 °C), as proved by the steady-state polarization measurements. Particularly, linear correlation was presented between the output current of the senor and the methanol concentration from 0 to 2 M. The stability test shows that the sensor has an average degradation rate as low as 1.22 mA cm−2 h−1. Therefore, the as-fabricated sensor shows a promising application in DMFCs in terms of its high sensitivity, high stability and the merits of simple processing, fabrication and low cost.Highlights► A novel miniaturized electrochemical methanol sensor. ► High sensitivity. ► High stability. ► Simple processing and fabrication.
Co-reporter:Yunjie Huang, Qingfeng Li, Annemette H. Jensen, Min Yin, Jens Oluf Jensen, Erik Christensen, Chao Pan, Niels J. Bjerrum and Wei Xing
Journal of Materials Chemistry A 2012 vol. 22(Issue 42) pp:22452-22458
Publication Date(Web):31 Aug 2012
DOI:10.1039/C2JM34704K
A new proton conductor based on niobium phosphates was synthesized using niobium pentoxide and phosphoric acid as precursors. The existence of hydroxyl groups in the phosphates was confirmed and found to be preserved after heat treatment at 500 °C or higher, contributing to an anhydrous proton conductivity of 1.6 × 10−2 S cm−1 at 250 °C. The conductivity increased with water content in the atmosphere and reached 5.8 × 10−2 S cm−1 under pure water vapour at the same temperature. The conductivity showed good stability in the low water partial pressure range of up to 0.05 atm. The metal phosphates are of high interest as potential proton conducting electrolytes for fuel cells operational in an intermediate temperature range.
Co-reporter:Xiao Zhao, Jianbing Zhu, Liang Liang, Jianhui Liao, Changpeng Liu and Wei Xing
Journal of Materials Chemistry A 2012 vol. 22(Issue 37) pp:19718-19725
Publication Date(Web):03 Aug 2012
DOI:10.1039/C2JM33926A
The development of advanced support materials displays the potential for both reducing the cost and simultaneously increasing the activity of catalysts. In the current work, a novel N-doped carbon coated hydrophilic titanium dioxide (TiO2@N-doped C) nano-composite, constructed by the procedure of an in situ polymerization and subsequent pyrolysis, was utilized to support Pt nano-crystals for the methanol oxidation reaction (MOR). The as-prepared Pt/TiO2@N-doped C catalyst generated 1.74-fold higher activity, 2.08-fold higher stability and much better resistance to CO poisoning than a commercial state-of-the-art Pt/C catalyst. The enhanced catalytic performance was ascribed to the improved CO tolerance and the catalyst–support interaction due to the utilization of the TiO2@N-doped C nano-composite, which not only provides rich active –OH groups to promote CO oxidation via the bifunctional mechanism, but also modifies the electronic structure of the Pt NPs to improve the intrinsic kinetics of MOR. The as-developed TiO2@N-doped C nano-composite is a highly promising catalyst support material for use in fuel cell technology.
Co-reporter:Ligang Feng, Xiujuan Sun, Changpeng Liu and Wei Xing
Chemical Communications 2012 vol. 48(Issue 3) pp:419-421
Publication Date(Web):26 Oct 2011
DOI:10.1039/C1CC16522D
A surprisingly high and stable current was observed after the peak current on the PdHoOx/C catalyst indicating the diminished poisoning effect. Moreover, the novel PdHoOx/C catalyst exhibited excellent catalytic activity and stability for formic acid oxidation due to the large electrochemical surface area and electronic effect.
Co-reporter:Yuwei Zhang, Weiwei Cai, Fengzhan Si, Junjie Ge, Liang Liang, Changpeng Liu and Wei Xing
Chemical Communications 2012 vol. 48(Issue 23) pp:2870-2872
Publication Date(Web):20 Jan 2012
DOI:10.1039/C2CC17230E
We developed a method to significantly decrease the methanol permeability of a Nafion membrane that does not require sacrificing its proton conductivity and mechanical stability. The Nafion membrane modified by the coating of a thin layer of sulfonated organic silica on the membrane surface exhibits significantly decreased methanol permeability—the permeability is decreased to an undetectable level—while retaining an acceptable ionic conductivity of 0.029 S cm−1.
Co-reporter:Qing Lv, Min Yin, Xiao Zhao, Chenyang Li, Changpeng Liu, Wei Xing
Journal of Power Sources 2012 Volume 218() pp:93-99
Publication Date(Web):15 November 2012
DOI:10.1016/j.jpowsour.2012.06.051
TiO2 and C are mixed up physically as hybrid support of Pt nanoparticles for methanol electrooxidation. The morphology and electrocatalytic properties of the as-obtained catalysts have been investigated by transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry and chronoamperometry. The catalytic activity and stability of Pt/TiO2–C catalyst are both improved markedly compared with that of Pt/C catalyst. The initial and final current of Pt/TiO2–C catalyst after 3600 s reactions for methanol oxidation is about 1.57 and 6 times as high as that of the Pt/C catalyst, respectively. The promotion effect of TiO2 on catalytic activity and stability for Pt/TiO2–C catalyst is investigated further by physical and electrochemical measurements. It is found that the addition of TiO2 could facilitate CO removal, hinder CO formation on Pt surface during methanol oxidation, and inhibit the agglomeration and corrosion of Pt particles, which can be resulted from the strong interaction between TiO2–C and Pt.Highlights► C and TiO2 are mixed up physically as the hybrid support of Pt. ► Methanol oxidation activity and stability on Pt/TiO2–C catalyst were improved. ► Pt and TiO2 interaction facilitates CO removal and hinders CO formation during methanol oxidation. ► The promotion effect should be attributed to the presence of TiO2.
Co-reporter:Ligang Feng, Shikui Yao, Xiao Zhao, Liang Yan, Changpeng Liu, Wei Xing
Journal of Power Sources 2012 Volume 197() pp:38-43
Publication Date(Web):1 January 2012
DOI:10.1016/j.jpowsour.2011.09.030
It is found that the electrocatalytic activity and stability of Pd/C nanocatalyst for formic acid electrooxidation are enhanced by the introduction of EuOx. The morphology, composition and electrocatalytic properties of the PdEuOx/C catalyst are investigated by the transmission electronmicroscopy, energy dispersive X-ray analysis, X-ray diffraction, the linear sweep voltammetry and chronoamperometry, respectively. The EDX results confirm the existence of EuOx in the PdEuOx/C catalysts. The XRD results indicate that the Pd is in the state of face-centered cubic phase structure. The linear sweeping voltammetry and chronoamperometry measurements show that the current of formic acid electrooxidation on the PdEuOx/C catalyst is ca. 2.5 times and 9 times as high as that of the home-made Pd/C catalyst, respectively; moreover, the performances are also much higher than the commercial Pd/C catalyst. The high performances can be attributed to the larger electrochemical surface area and the electronic effect of the EuOx in the PdEuOx/C catalyst.Highlights► EuOx was introduced into Pd/C catalyst for formic acid oxidation. ► PdEuOx/C catalyst was characterized by XRD, EDX and XPS. ► Formic acid oxidation activity and stability on PdEuOx/C catalyst were improved.
Co-reporter:Min Yin, Qingfeng Li, Jens Oluf Jensen, Yunjie Huang, Lars N. Cleemann, Niels J. Bjerrum, Wei Xing
Journal of Power Sources 2012 Volume 219() pp:106-111
Publication Date(Web):1 December 2012
DOI:10.1016/j.jpowsour.2012.07.032
Tungsten carbide (WC) promoted palladium (Pd) and palladium–cobalt (Pd–Co) nanocatalysts are prepared and characterized for formic acid electrooxidation. The WC as the dopant to carbon supports is found to enhance the CO tolerance and promote the activity of the Pd-based catalysts for formic acid oxidation. Alloying of Pd with Co further improves the electrocatalytic activity and stability of the WC supported catalysts, attributable to a synergistic effect of the carbide support and PdCo alloy nanoparticles.Highlights► Carbon support functionalized by facilely obtained tungsten carbide. ► Palladium-based nanoparticles supported on the functionalized carbon synthesized. ► Superior activity and stability achieved with the PdCo/WC-C catalyst. ► Synergetic effects among Pd, Co ad WC proposed for the catalytic process.
Co-reporter:Shikui Yao, Ligang Feng, Xiao Zhao, Changpeng Liu, Wei Xing
Journal of Power Sources 2012 Volume 217() pp:280-286
Publication Date(Web):1 November 2012
DOI:10.1016/j.jpowsour.2012.05.120
A simple, environment-friendly and aqueous-route colloidal-precipitation method is successfully employed to prepare carbon supported platinum nanoparticles with a narrow size distribution. In this method, (NH4)2WO4 is used to react with H2PtCl6, which forms the (NH4)2PtCl6 and H2WO4 simultaneously. The precipitation of (NH4)2PtCl6 and the colloidal of H2WO4 can protect the formation of the Pt nanoparticles. Transmission electron microscopy demonstrates that the Pt nanoparticles with a narrow size distribution are well dispersed on the carbon support. More importantly, the size of the Pt nanoparticles can be simply controlled by tuning the concentration of (NH4)2WO4 and the Pt nanoparticles prepared in the 0.5 mmol L−1 (NH4)2WO4 exhibit the smallest size of ca. 3 nm. Further, cyclic voltammetric and chronoamperometric experiments show that the prepared Pt/C catalyst exhibited excellent catalytic activity and stability compared with the Pt/C prepared by impregnation method and the state-of-the-art commercial Pt/C. For example, the peak current and the stable current at 3600 s of the Pt/C catalyst prepared with the 0.5 mmol L−1 (NH4)2WO4 is about 1.24 and 1.78 times of the commercial Pt/C. Therefore, the as-proposed colloidal-precipitation method exhibits a potential application in preparing highly dispersive and electroactive Pt/C catalysts for direct methanol fuel cells.Highlights► Colloidal-precipitation method was explored to prepare Pt/C. ► The prepared Pt nanoparticles dispersed well and had a narrow size distribution. ► Particle size of the Pt can be well controlled. ► The Pt/C showed enhanced activity and stability for methanol electrooxidation.
Co-reporter:Weiwei Cai, Liang Yan, Chenyang Li, Liang Liang, Wei Xing, Changpeng Liu
International Journal of Hydrogen Energy 2012 Volume 37(Issue 4) pp:3425-3432
Publication Date(Web):February 2012
DOI:10.1016/j.ijhydene.2011.10.120
A medium-scale DFAFC stack was designed and fabricated in this work. The power output of this stack was high to 32 W, which can satisfy the power requirement of most portable electrical devices. The ultrasonically mixed Pt/C + Pd/C catalyst was optimized as the anode catalyst for the stack fabrication by using a single cell. The feeding formic acid concentration and oxygen flow rate respectively in anode and cathode side were also experimentally optimized before the stack fabrication. Under the optimal operation conditions, the life time test was carried out for the DFAFC stack using the optimal anode catalyst. The stack can stably operate for about 50 h with 1.5 L fuel supplied, and its high durability was confirmed by the 240 h continuous life time test.Highlights► Power output was high to 32 W ► The stack can stably operate for about 240 h ► The ultrasonically mixed Pt/C + Pd/C catalyst was optimized as the anode catalyst. ► Operation conditions were optimized for the stack.
Co-reporter:Ligang Feng, Jing Yang, Yang Hu, Jianbing Zhu, Changpeng Liu, Wei Xing
International Journal of Hydrogen Energy 2012 Volume 37(Issue 6) pp:4812-4818
Publication Date(Web):March 2012
DOI:10.1016/j.ijhydene.2011.12.114
The PdCeOx/C catalyst was prepared and studied as anodic catalyst for formic acid electrooxidation. The morphology, composition and electrocatalytic properties were investigated by transmission electronmicroscopy, energy dispersive X-ray analysis, X-ray diffraction, X-ray photoelectron spectroscopy, the linear sweep voltammetry and chronoamperometry, respectively. The average particle size of Pd nanoparticles for PdCeOx/C catalyst was about 3.4 nm with a narrow size distribution. The electrochemical surface area (ESA) of PdCeOx/C catalyst was larger than the Pd/C catalyst. According to the Tafel plots, the presence of CeOx in the Pd/C catalyst can accelerate the rate of formic acid electrooxidation. The electrochemical measurements showed that the PdCeOx/C catalyst exhibited excellent catalytic activity and stability. For example, the peak current of PdCeOx/C catalyst for formic acid oxidation was about 1.67 times of the Pd/C catalyst and the stable current at 3600 s of PdCeOx/C catalyst was about 7 times of the Pd/C catalyst. The promotion effect should be attributed to the larger ESA, the electronic effect and more oxygen-containing species provided by the CeOx and this catalyst may be used as an effective catalyst for direct formic acid fuel cell.Highlights► PdCeOx/C catalyst was studied for formic acid electrooxidation. ► CeOx in Pd/C catalyst can accelerate the rate of formic acid oxidation. ► Formic acid oxidation activity and stability on PdCeOx/C catalyst were improved. ► The promotion effect should be attributed to the presence of CeOx.
Co-reporter:Xiao Zhao, Yang Hu, Liang Liang, Changpeng Liu, Jianhui Liao, Wei Xing
International Journal of Hydrogen Energy 2012 Volume 37(Issue 1) pp:51-58
Publication Date(Web):January 2012
DOI:10.1016/j.ijhydene.2011.09.075
Uniform Pd nanoparticles supported on Vulcan XC-72 carbon were successfully synthesised at room temperature using an ionic liquid (IL) as a mediator for the nucleation and growth process. The UV–vis spectra indicated that the IL interacted with the Pd precursor to form a complex that plays an important role in the nucleation and growth process of Pd nanoparticles. The IL-mediated synthesis of the Pd/C catalyst (Pd/C-IL) was extensively characterised by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, electrochemical COad stripping, linear scanning voltammetry and chronoamperometry. Physical characterisations revealed that the Pd/C-IL had an average size of 2.8 nm and a narrow size distribution. In addition, a very ‘clean’ surface was obtained for the Pd nanoparticles due to a weak interaction between the IL and the Pd nanoparticle surface resulting in the facile removal of the IL in the post-treatment process. More importantly, electrochemical studies demonstrated that, at an operating potential of 0.2 V, the catalytic activity of the Pd/C-IL was approximately 1.6 and 4.2-fold greater than the commercial Pd/C catalyst and the common Pd/C catalyst, respectively.Highlights► Ionic liquid as a mediator for the synthesis of Pd nanoparticles. ► Uniform and ‘clean’ Pd nanoparticles were successfully obtained. ► Improved mass activity was obtained for formic acid electrooxidation.
Co-reporter:Fengzhan Si, Liang Ma, Changpeng Liu, Xinbo Zhang and Wei Xing
RSC Advances 2012 vol. 2(Issue 2) pp:401-403
Publication Date(Web):04 Nov 2011
DOI:10.1039/C1RA00326G
High-loading carbon supported Pt nanowire electrocatalysts are successfully synthesized in a mild one-pot template- and surfactant-free route. The high electrocatalytic activity, Pt utilization, and long-term stability toward methanol are ascribed to the anisotropic structural properties, exposure of specified planes, and the role of support on good dispersion.
Co-reporter:Ligang Feng, Qing Lv, Xiujuan Sun, Shikui Yao, Changpeng Liu, Wei Xing
Journal of Electroanalytical Chemistry 2012 Volume 664() pp:14-19
Publication Date(Web):1 January 2012
DOI:10.1016/j.jelechem.2011.10.006
The Keggin-structure molybdovanadophosphoric acid (H3+xPMo12−xVxO40, x = 1, 2, 3, denoted as PMV) modified Pt electrode was studied by electrochemical measurements for methanol oxidation. It was discovered that both the catalytic activity and stability of the PMV modified Pt electrode were significantly enhanced. With the increase of the vanadium content in PMV, the catalytic activity and stability for methanol electrooxidation were also increased. The enhancements were attributed to the special properties of PMV, which increased the electron transfer coefficient of the rate-determining step. Therefore, the PMV has potential application as promoter for methanol electrooxidation in direct methanol fuel cell.Highlights► The PMV modified Pt electrode enhanced the performances for methanol oxidation. ► The Pt–V3 electrode has the best catalytic activity. ► The electron transfer coefficient was increased on the PMV modified Pt electrode. ► The enhancements were attributed to the special properties of PMV.
Co-reporter:Kunqi Wang, Jing Yang, Ligang Feng, Yuwei Zhang, Liang Liang, Wei Xing, Changpeng Liu
Biosensors and Bioelectronics 2012 Volume 32(Issue 1) pp:177-182
Publication Date(Web):15 February 2012
DOI:10.1016/j.bios.2011.11.056
Electrical energy generated directly from sunlight and biomass solution with a Photoelectrochemical Biofuel Cell (PEBFC) was investigated. The PEBFC consisted of a meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP)-sensitized nanocrystalline titanium dioxide (TiO2) mesoporous film (NTDMF) as the photoanode and platinum black as the cathode. The interaction between TCPP sensitizer and NTDMF was evaluated by X-ray photoelectron spectra and FT-IR absorption spectra, indicating that the TCPP sensitizer was adsorbed on the NTDMF by bridging or bidentate coordinate bonds. The spectroscopic properties of pure TCPP ethanol solution and TCPP-sensitized NTDMF were obtained by UV–vis absorption spectra, demonstrating that the characteristic absorption peaks of TCPP on NTDMF displayed slight red shift compared with pure TCPP ethanol solution. The performances of the PEBFC were obtained by photocurrent–photovoltage characteristic curves. The open-circuit photovoltage (Voc), the short-circuit photocurrent (Isc) and the maximum power density (Pmax) was 0.74 V, 69.96 μA and 33.94 μW cm−2 at 0.45 V, respectively. The fill factor (FF) was 0.19 and the incident photo-to-current efficiency (IPCE) was 36.0% at 436 nm. The results demonstrated that the TCPP was an appropriate photosensitizer for PEBFC.Highlights► We have constructed a novel photoelectrochemical biofuel cell (PEBFC). ► Meso-tetrakis (4-carboxyphenyl)porphyrin(TCPP) is anodic sensitizer of the PEBFC. ► TCPP has been immobilized on TiO2 by bridging or bidentate coordinate bonds. ► Open-circuit photovoltage of the PEBFC is 0.74 V. ► Maximum power density of the PEBFC is 33.94μW cm−2.
Co-reporter:Xiao Zhao, Min Yin, Liang Ma, Liang Liang, Changpeng Liu, Jianhui Liao, Tianhong Lu and Wei Xing
Energy & Environmental Science 2011 vol. 4(Issue 8) pp:2736-2753
Publication Date(Web):11 Jul 2011
DOI:10.1039/C1EE01307F
Over the past few decades, direct methanol fuel cells (DMFCs) have been intensively developed as clean and high-efficiency energy conversion devices. However, their dependence on expensive Pt-based catalysts for both the anode and the cathode make them unsuitable for large-scale commercialisation. The essential solution to addressing this shortfall is the development of low-Pt and non-Pt catalysts. Regarding this issue, considerable advances have been made with low-Pt alloys and core-shell-like catalysts, as well as non-platinum Pd–Me, Ru–Se and heat-treated MeNxCy-based catalysts. This perspective reviews potential pathways for increasing the cost-effectiveness and efficiency of these catalysts. Fundamental understanding of the composition–activity and structure–activity relationships, innovative synthesis, and promising developmental directions are highlighted. Regarding durability, the main degradation mechanism of these catalysts and the corresponding mitigating strategies are presented.
Co-reporter:Min Yin, Yunjie Huang, Liang Liang, Jianhui Liao, Changpeng Liu and Wei Xing
Chemical Communications 2011 vol. 47(Issue 28) pp:8172-8174
Publication Date(Web):20 Jun 2011
DOI:10.1039/C1CC12561C
CO poisoning during methanol electrooxidation was investigated on PtAu alloys with different surface compositions. Results show that the CO formation can be reduced gradually with increasing surface Au fractions in PtAu alloys and CO poisoning can be almost eliminated by adjusting to a proper surface Au fraction.
Co-reporter:Weiwei Cai, Songtao Li, Liang Yan, Ligang Feng, Jing Zhang, Liang Liang, Wei Xing, Changpeng Liu
Journal of Power Sources 2011 Volume 196(Issue 18) pp:7616-7626
Publication Date(Web):15 September 2011
DOI:10.1016/j.jpowsour.2011.05.006
This study investigates an aqueous solution of sulfuric acid that serves as the liquid electrolyte (LE) in a passive direct methanol fuel cell (DMFC). The addition of an LE can reduce methanol crossover and increase the fuel utilization significantly. To improve the performance of an LE-DMFC, a mathematical model is developed to optimize the thicknesses of both the LE layer and the Nafion membrane. The maximum power density of the LE-DMFC is improved by approximately 30% compared with a conventional DMFC (C-DMFC) when each is fed by methanol solutions of the same concentration. Due to the low methanol crossover of the LE-DMFC, a highly concentrated methanol solution can be directly fed into the LE-DMFC. The discharge time and volume energy density of the LE-DMFC are two times longer and three times greater than those of the C-DMFC, respectively. In addition, fuel utilization increases by approximately 100%.Highlights► LE-DMFC has a 30% lager maximum power density than C-DMFC with the same methanol concentration. ► The LE-DMFC can be fed with high concentration methanol. ► The LE-DMFC can obtain an energy density higher than 110 Wh L−1. ► The LE-DMFC has a 100% higher fuel utilization than C-DMFC with the same methanol concentration.
Co-reporter:Zhiming Cui, Ligang Feng, Changpeng Liu, Wei Xing
Journal of Power Sources 2011 Volume 196(Issue 5) pp:2621-2626
Publication Date(Web):1 March 2011
DOI:10.1016/j.jpowsour.2010.08.118
A simple and novel method for the preparation of WO3/C is presented. This method includes the adsorption and decomposition of phosphotungstic acid (PWA) on carbon. For the purpose of comparison, WO3/C is also prepared by a conventional method using sodium tungstate as the precursor. These two WO3/C species are denoted as WO3/C-1 and WO3/C-2, respectively. It is shown from transmission electron microscopy (TEM) that the WO3 particles in WO3/C-1 present a more even distribution and smaller particle size than those in WO3/C-2. Pt particles dispersed on WO3/C-1 display the characteristic diffraction peaks of Pt in the face-centered cubic phase. Cyclic voltammetry and chronoamperometry show that the Pt–WO3/C-1 catalyst exhibits much better methanol oxidation activity than the Pt–WO3/C-2 and Pt/C catalysts. This significant improvement in catalytic performance may be attributed to the hydrogen spillover effect and the uniform distribution of Pt and WO3 particles.
Co-reporter:Ligang Feng, Liang Yan, Zhiming Cui, Changpeng Liu, Wei Xing
Journal of Power Sources 2011 Volume 196(Issue 5) pp:2469-2474
Publication Date(Web):1 March 2011
DOI:10.1016/j.jpowsour.2010.11.073
Pd nanoparticles supported on the WO3/C hybrid are prepared by a two-step procedure and the catalysts are studied for the electrooxidation of formic acid. For the purpose of comparison, phosphotungstic acid (PWA) and sodium tungstate are used as the precursor of WO3. Both the Pd–WO3/C catalysts have much higher catalytic activity for the electrooxidation of formic acid than the Pd/C catalyst. The Pd–WO3/C catalyst prepared from PWA shows the best catalytic activity and stability for formic acid oxidation; it also shows the maximum power density of approximately 7.6 mW cm−2 when tested with a small single passive fuel cell. The increase of electrocatalytic activity and stability is ascribed to the interaction between the Pd and WO3, which promotes the oxidation of formic acid in the direct pathway. The precursors used for the preparation of the WO3/C hybrid support have a great effect on the performance of the Pd–WO3/C catalyst. The WO3/C hybrid support prepared from PWA is beneficial to the dispersion of Pd nanoparticles, and the catalyst has potential application for direct formic acid fuel cell.Research highlights▶ Pd–WO3/C catalyst prepared from PWA shows the best catalytic activity and stability for formic acid oxidation. ▶ The increase of electrocatalytic activity and stability is ascribed to the interaction between Pd and WO3, which promotes the oxidation of formic acid in direct pathway. ▶ The precursors used for the preparation of WO3/C hybrid support have a great effect on the performance of Pd–WO3/C catalyst.
Co-reporter:Ligang Feng, Jing Zhang, Weiwei Cai, Liangliang, Wei Xing, Changpeng Liu
Journal of Power Sources 2011 Volume 196(Issue 5) pp:2750-2753
Publication Date(Web):1 March 2011
DOI:10.1016/j.jpowsour.2010.11.125
A new single passive direct methanol fuel cell (DMFC) supplied with pure methanol is designed, assembled and tested using a pervaporation membrane (PM) to control the methanol transport. The effect of the PM size on the fuel cell performances and the constant current discharge of the fuel cell with one-fueling are studied. The results show that the fuel cell with PM 9 cm2 can yield a maximum power density of about 21 mW cm−2, and a stable performances at a discharge current of 100 mA can last about 45 h. Compared with DMFC supplied with 3 M methanol solution, the energy density provided by this new DMFC has increased about 6 times.Research highlights▶ A new single passive DMFC supplied with pure methanol using a PM to control the methanol transport is designed and tested. ▶ The maximum power density of about 21 mW cm−2 is obtained with the PM size of 9 cm2. ▶ Compared with the DMFC supplied with 3 M methanol solution, the energy density provided by this new DMFC has increased about 6 times.
Co-reporter:Weiwei Cai, Songtao Li, Ligang Feng, Jing Zhang, Datong Song, Wei Xing, Changpeng Liu
Journal of Power Sources 2011 Volume 196(Issue 8) pp:3781-3789
Publication Date(Web):15 April 2011
DOI:10.1016/j.jpowsour.2010.12.083
A new structure of passive direct methanol fuel cell (DMFC) with two methanol reservoirs separated by a porous medium layer is designed and a corresponding mathematical model is presented. The new designed passive DMFC can be directly fed with highly concentrated methanol solution or neat methanol. The porosity (ɛpr) of the porous medium layer is optimized using the proposed model. Some operation parameters are also optimized by both the numerical calculation and experimental measurement. The new designed DMFC can be continuously operated for about 4.5 times longer than a conventional passive DMFC with the optimum parameters. The methanol crossover during the same discharging is only about 50% higher.Research highlights▶ A passive DMFC is manufactured for high concentration or neat methanol feeding. ▶ This design wouldn’t increase the CO2 releasing resistance. ▶ The new DMFC can continuously operate about 4.5 times longer than a conventional DMFC.
Co-reporter:Jing Zhang, Ligang Feng, Weiwei Cai, Changpeng Liu, Wei Xing
Journal of Power Sources 2011 Volume 196(Issue 22) pp:9510-9515
Publication Date(Web):15 November 2011
DOI:10.1016/j.jpowsour.2011.07.039
Homemade wet-proofing carbon papers with back-flow effect were applied as backing layers in the cathode of passive air-breathing direct methanol fuel cell (DMFC) fed by pure methanol. With the increase of polytetrafluoroethylene (PTFE) content, the carbon papers exhibited different water transport resistance and generated different back-flow effects. Moreover, PTFE-treated carbon papers were observed by scanning electronic microscope (SEM) to investigate the function of the cross-linked microstructure. Maximum energy density (438 Wh L−1) of the improved pure methanol DMFC was obtained by using carbon paper with 40 wt.% PTFE content as the cathodic backing layer. This value was 6 times larger than that of the conventional DMFC fed by 2 M methanol solution.Highlights► Investigation of water transport resistance and hydrophobicity on carbon paper. ► Hydrophobicity gradient to accelerate the back-flow effect. ► Long-time operation of DMFC with pure methanol and high output energy density.
Co-reporter:Min Yin, Yunjie Huang, Qing Lv, Liang Liang, Jianhui Liao, Changpeng Liu, Wei Xing
Electrochimica Acta 2011 Volume 58() pp:6-11
Publication Date(Web):30 December 2011
DOI:10.1016/j.electacta.2011.08.002
The PtAu/C alloy catalyst is firstly synthesized by the co-reduction of both metal precursors under microwave conditions and then heat-treated to enable the migration of Au atoms to the exterior surface of the obtained PtAu/C catalyst. The bulk crystallite structures and the surface Au contents of PtAu/C catalysts are characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The electrocatalytic activity and durability measurements exhibit the superior catalytic performance of PtAu/C catalysts over that of Pt/C catalyst on formic acid electrooxidation. Moreover, the initial and final activity after 3600 s reaction of the heat-treated PtAu/C alloy catalyst is two and five times as high as that of the untreated PtAu/C catalyst. The performance enhancement of the PtAu/C catalysts is discussed in terms of the electronic effect and ensemble effect.Highlights► PtAu/C alloy catalyst is obtained by microwave-assisted polyol reduction method. ► Heat treatment is performed successfully to increase Au fraction on PtAu surface. ► The direct electrooxidation of HCOOH is improved on the heat treated catalyst. ► Both activity and durability of heat treated catalyst are improved greatly. ► The superior performance of heat treated catalyst is attributed to the improved ensemble effect resulted from the increased interrupting Pt sites in the presence of more Au atoms on PtAu surface.
Co-reporter:Fengzhan Si, Xiumei Chen, Liang Liang, Chenyang Li, Jianhui Liao, Changpeng Liu, Xinbo Zhang, Wei Xing
Electrochimica Acta 2011 Volume 56(Issue 17) pp:5966-5971
Publication Date(Web):1 July 2011
DOI:10.1016/j.electacta.2011.04.106
Two types of Pt nanowires (NWs)/C catalysts with different aspect ratios and one type of Pt nanoparticles/C catalyst are successfully synthesized, and DME electrochemical performance on different extent consecutive surfaces is investigated. The morphology and crystallization are confirmed with electron microscopes and XRD. The electrochemical tests show that the nanowire catalysts, especially the one with higher aspect ratio, possess higher electrochemical surface areas, higher absorption capacity of DME, higher CO tolerance, higher electron transfer coefficient, and higher activity towards DME electrooxidation than those of the nanoparticle catalyst. The results prove that the consecutive surface favors for direct dimethyl ether fuel cell (DDFC) anodic catalyst, which are contributive to the study of the mechanism of DME electrooxidation on Pt surface and designing an effective catalyst for anodic DDFC.Highlights► Pt/C catalysts with different morphologies are designed and synthesized. ► The support and reaction temperature are important in morphology and aspect ratio. ► The relationship between consecutive surface and performance is investigated.
Co-reporter:Yunjie Huang, Xiaochun Zhou, Min Yin, Changpeng Liu, and Wei Xing
Chemistry of Materials 2010 Volume 22(Issue 18) pp:5122
Publication Date(Web):August 25, 2010
DOI:10.1021/cm101285f
A novel PdAu bimetallic catalyst with a PdAu@Au core−shell nanostructure supported on carbon was facilely synthesized by a simultaneous reduction method without using any stabilizer. The structure was characterized by cyclic voltammetry, X-ray diffraction, transmission electron microscopy (TEM), and high-angle annular dark-field scanning TEM combining with X-ray energy-dispersive spectroscopy. The obtained catalyst was applied in hydrogen generation from formic acid decomposition. Results show that the structured bimetallic catalyst possesses superior activity, high selectivity, and stability at low temperature. The reforming gas from formic acid decomposition contains only 30 ppm of CO and can be used directly in fuel cell.
Co-reporter:Zhiming Cui, Wei Xing, Changpeng Liu, Dan Tian, Hong Zhang
Journal of Power Sources 2010 Volume 195(Issue 6) pp:1619-1623
Publication Date(Web):15 March 2010
DOI:10.1016/j.jpowsour.2009.09.040
Pt/C(a) catalysts are firstly prepared by modified impregnation method. In order to enhance the ability of Pt/C catalysts for methanol electrooxidation, H5PMo10V2O40 (PMV) is adsorbed on Pt/C catalysts to obtain the PMV-Pt/C catalysts. The Pt/C(a) and PMV-Pt/C are characterized by transmission electron microscopy (TEM) and X-ray diffractometry. It is shown that Pt particles with small average size are uniformly disperesed on carbon. Cyclic voltammetry and chronoamperometry show that the PMV-Pt/C catalysts exhibit excellent catalytic activity and stability for methanol electrooxidation.
Co-reporter:Yuwei Zhang, Junjie Ge, Zhiming Cui, Changpeng Liu, Wei Xing, Jiujun Zhang, Haidan Lin, Hui Na
International Journal of Hydrogen Energy 2010 Volume 35(Issue 15) pp:8337-8342
Publication Date(Web):August 2010
DOI:10.1016/j.ijhydene.2009.12.006
A series of sulphonated poly (ether ether ketone) (sPEEK) membranes for direct methanol fuel cells are successfully prepared under different humidity degree conditions. These membranes exhibit enhanced proton conductivity at high humidity degree. It is proved that the different proton conductivity is ascribed to the orientation arrangement of sulphonic acid groups, which is caused by environmental water in the preparing process of membranes. A model is established by analyzing the dynamics of membrane formation and proved by Field emission scanning electron microscopy (ESEM) and X-ray photoelectron spectroscopy (XPS).
Co-reporter:Dr. Xiaochun Zhou;Dr. Yunjie Huang; Changpeng Liu; Jianhui Liao; Tianhong Lu ; Wei Xing
ChemSusChem 2010 Volume 3( Issue 12) pp:1379-1382
Publication Date(Web):
DOI:10.1002/cssc.201000199
Co-reporter:Haidan Lin, Chengji Zhao, Zhiming Cui, Wenjia Ma, Tiezhu Fu, Hui Na, Wei Xing
Journal of Power Sources 2009 Volume 193(Issue 2) pp:507-514
Publication Date(Web):5 September 2009
DOI:10.1016/j.jpowsour.2009.04.036
A novel strategy in which the benzimidazole group and sulfonic group are simultaneously attached to an aromatic polymer has been reported in this paper. For this purpose, sulfonated poly(arylene ether ketone) copolymers containing carboxylic acid groups (SPAEK-x-COOH, x refers to the molar percentage of sulfonated repeating units) are prepared by the aromatic nucleophilic polycondensation of sodium 5,5′-carbonyl-bis(2-fluobenzene-sulfonate) (SDFBP), 4,4′-difluorobenzophenone (DFBP) and phenolphthalin (PPL). Then the carboxylic acid groups attached to the SPAEK-x-COOH are transformed to benzimidazole units through condensation reactions (referred to as SPAEK-x-BI). Fourier transform infrared spectroscopy and 1H NMR measurements are used to characterize and confirm the structures of these copolymers. SPAEK-x-COOH membranes exhibit superior mechanical properties with maximum elongations at break up to 133%, meanwhile SPAEK-x-BI also shows good thermal and mechanical stability. The proton conductivity, swelling ratio and methanol permeability of the polymers with benzimidazole are lower than those with carboxylic groups, which indicated that there is an acid–base complex between benzimidazole and sulfonic acid groups. A balance of proton conductivity, methanol permeability, thermal and mechanical stabilities can be designed by incorporation of functional groups to meet the requirements for the applications in direct methanol fuel cells.
Co-reporter:Hongtao Li, Zhiming Cui, Chengji Zhao, Jing Wu, Tiezhu Fu, Yang Zhang, Ke Shao, Haiqiu Zhang, Hui Na, Wei Xing
Journal of Membrane Science 2009 Volume 343(1–2) pp:164-170
Publication Date(Web):1 November 2009
DOI:10.1016/j.memsci.2009.07.021
Bisphenol monomer 4-carboxylphenyl hydroquinone (4C-PH) containing carboxyl groups was synthesized by diazotization reaction of p-aminobenzoic acid and 1,4-benzoquinone and subsequent reductive reaction. Copolymerization of bisphenol A, 4C-PH, sodium 5,5′-carbonylbis(2-fluorobenzene-sulfonate) and 4,4′-difluorobenzophenone at various molar ratios through aromatic nucleophilic substitution reaction resulted in a new sulfonated poly(ether ether ketone) containing pendant carboxyl groups (C-SPEEK). The structures of the monomer 4C-PH and copolymers were confirmed by FT-IR and 1H NMR. Flexible and transparent membranes with sulfonic and carboxylic acid groups as the proton conducting sites were prepared. The dependence of ion-exchange capacity (IEC), water uptake, proton conductivity and methanol permeability on the degree of sulfonation has been studied. The highest proton conductivity of 0.16 S cm−1 was obtained from C-SPEEK-4 (IEC = 1.44 mequiv. g−1) at 80 °C, higher than that of Nafion117 (0.12 S cm−1). Incorporating carboxylic acid groups into copolymers led to higher dimensional stability and lower water uptake. The methanol permeability coefficients of C-SPEEK membranes were in the range of 3.54 × 10−7 cm2 s−1 to 5.9 × 10−9 cm2 s−1, which were significantly lower than that of Nafion117 (1.61 × 10−6 cm2 s−1). Accordingly, the C-SPEEK membranes exhibited much higher selectivity (conductivity/methanol permeability coefficient) compared with Nafion117 membrane.
Co-reporter:Zhiming Cui, Wei Xing, Changpeng Liu, Jianhui Liao, Hong Zhang
Journal of Power Sources 2009 Volume 188(Issue 1) pp:24-29
Publication Date(Web):1 March 2009
DOI:10.1016/j.jpowsour.2008.11.108
As inorganic proton conductors, phosphomolybdic acid (PMA), phosphotungstic acid (PWA) and silicotungstic acid (SiWA) are extremely attractive for proton-conducting composite membranes. An interesting phenomenon has been found in our previous experiments that the mixing of chitosan (CS) solution and different heteropolyacids (HPAs) leads to strong electrostatic interaction to form insoluble complexes. These complexes in the form of membrane (CS/PMA, CS/PWA and CS/SiWA composite membranes) have been prepared and evaluated as novel proton-conducting membranes for direct methanol fuel cells. Therefore, HPAs can be immobilized within the membranes through electrostatic interaction, which overcomes the leakage problem from membranes. CS/PMA, CS/PWA and CS/SiWA composite membranes were characterized for morphology, intermolecular interactions, and thermal stability by SEM, FTIR, and TGA, respectively. Among the three membranes, CS/PMA membrane was identified as ideal for DMFC as it exhibited low methanol permeability (2.7 × 10−7 cm2 s−1) and comparatively high proton conductivity (0.015 S cm−1 at 25 °C).
Co-reporter:Yuwei Zhang, Zhiming Cui, Changpeng Liu, Wei Xing, Jiujun Zhang
Journal of Power Sources 2009 Volume 194(Issue 2) pp:730-736
Publication Date(Web):1 December 2009
DOI:10.1016/j.jpowsour.2009.06.022
A series of cost-effective, proton-conducting composite membranes, comprising of Nafion® ionomer, chitosan (CS), and polyvinyl alcohol (PVA), is successfully prepared. By taking advantage of the strong electrostatic interactions between Nafion® ionomer and CS component, Nafion ionomer is effectively implanted into the PVA/CS composite membranes, and improves proton conductivity of the PVA/CS composite membranes. Furthermore, this effect dramatically depends on the composition ratio of PVA/CS, and the optimum conductivity is obtained at the PVA/CS ratio of 1:1. The developed composite membranes exhibit much lower methanol permeability compared with the widely used Nafion® membrane, indicating that these novel membranes have great potential for direct methanol fuel cells (DMFCs).
Co-reporter:Yang Zhang, Zhiming Cui, Chengji Zhao, Ke Shao, Hongtao Li, Tiezhu Fu, Hui Na, Wei Xing
Journal of Power Sources 2009 Volume 191(Issue 2) pp:253-258
Publication Date(Web):15 June 2009
DOI:10.1016/j.jpowsour.2009.02.032
A series of novel side-chain-type sulfonated poly(arylene ether ketone)s with pendant carboxylic acid groups copolymers (C-SPAEKs) were synthesized by direct copolymerization of sodium 5,5′-carbonyl-bis(2-fluorobenzenesulfonate), 4,4′-difluorobenzophenone and 4,4′-bis(4-hydroxyphenyl) valeric acid (DPA). The expected structure of the sulfonated copolymers was confirmed by FT-IR and 1H NMR. Membranes with good thermal and mechanical stability could be obtained by solvent cast process. It should be noted that the proton conductivity of these copolymers with high sulfonatation degree (DS > 0.6) was higher than 0.03 S cm−1 and increased with increasing temperature. At 80 °C, the conductivity of C-SPAEK-3 (DS = 0.6) and C-SPAEK-4 (DS = 0.8) reached up to 0.12 and 0.16 S cm−1, respectively, which were higher than that of Nafion 117 (0.10 S cm−1). Moreover, their methanol permeability was much lower than that of Nafion 117. These results showed that the synthesized materials might have potential applications as the proton exchange membranes for DMFCs.
Co-reporter:Xiaogang Wang, Jianhui Liao, Changpeng Liu, Wei Xing, Tianhong Lu
Electrochemistry Communications 2009 Volume 11(Issue 1) pp:198-201
Publication Date(Web):January 2009
DOI:10.1016/j.elecom.2008.11.007
The PtRu/C electrocatalyst with high loading (PtRu of 60 wt%) was prepared by synergetic effect of ultrasonic radiation and mechanical stirring. Physicochemical characterizations show that the size of PtRu particles of as-prepared PtRu/C catalyst is only several nanometers (2–4 nm), and the PtRu nanoparticles were homogeneously dispersed on carbon surface. Electrochemistry and single passive direct methanol fuel cell (DMFC) tests indicate that the as-prepared PtRu/C electrocatalyst possessed larger electrochemical active surface (EAS) area and enhanced electrocatalytic activity for methanol oxidation reaction (MOR). The enhancement could be attributed to the synergetic effect of ultrasound radiation and mechanical stirring, which can avoid excess concentration of partial solution and provide a uniform environment for the nucleation and growth of metal particles simultaneously hindering the agglomeration of PtRu particles on carbon surface.
Co-reporter:Liang Ma, Changpeng Liu, Jianhui Liao, Tianhong Lu, Wei Xing, Jiujun Zhang
Electrochimica Acta 2009 Volume 54(Issue 28) pp:7274-7279
Publication Date(Web):1 December 2009
DOI:10.1016/j.electacta.2009.07.045
Co-reporter:Kunqi Wang, Hua Yang, Lin Zhu, Zhongsu Ma, Shenyang Xing, Qiang Lv, Jianhui Liao, Changpeng Liu, Wei Xing
Electrochimica Acta 2009 Volume 54(Issue 20) pp:4626-4630
Publication Date(Web):1 August 2009
DOI:10.1016/j.electacta.2009.02.097
In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified with mesoporous carbon FDU-15 (MC-FDU-15) and Nafion by simple technique. The sorption behavior of GOD immobilized on MC-FDU-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet–visible (UV–vis), FTIR, respectively, which demonstrated that MC-FDU-15 could facilitate the electron exchange between the active center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on the modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and MC-FDU-15 matrices display direct, reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 4.095 s−1 in 0.1 M phosphate buffer solution (PBS) (pH 7.12). Furthermore, it was also discovered that, in the presence of O2, GOD immobilized on Nafion and MC-FDU-15 matrices could produce a linear response to glucose. Thus, Nafion/GOD-MC-FDU-15/GC electrode is hopeful to be used in glucose biosensor. In addition, GOD immobilized on MC-FDU-15 and Nafion matrices possesses an excellent bioelectrocatalytic activity for the reduction of O2. So, the Nafion/GOD-MC-FDU-15/GC electrode can be utilized as the cathode in biofuel cell.
Co-reporter:Jing Wu, Zhiming Cui, Chengji Zhao, Hongtao Li, Yang Zhang, Tiezhu Fu, Hui Na, Wei Xing
International Journal of Hydrogen Energy 2009 Volume 34(Issue 16) pp:6740-6748
Publication Date(Web):August 2009
DOI:10.1016/j.ijhydene.2009.06.051
Composite membranes based on Sulfonated poly(ether ether ketone) (SPEEK) and sulfonated organically modified Si-SBA-15 (S-SBA-15) were investigated with the purpose of increasing the proton conductivity. The novelty of the composite membranes was attributed to two special structures and different ion exchange capacities (IEC) of S-SBA-15 fillers, which were embedded in membranes. The typical hexagonal channels array of S-SBA-15 was confirmed by XRD and TEM. The regular vermiculate and amorphous structures of the inorganic fillers were proved by SEM. Composite membranes were prepared through common solvent casting method. SEM images indicated that the inorganic filler with regular structure dispersed homogeneously in the composite membranes, but the amorphous filler caused an agglomeration phenomenon at the same loading content. The composite membranes exhibited good thermal stability, enhanced water uptake and proton conductivity. The proton conductivity of the composite membranes with low IEC filler was higher than the composite membranes with high IEC filler at the same loading content. The highest proton conductivity value of 0.156 S cm−1 was obtained for the composite membrane containing 5 wt.% S-SBA-15 with the IEC of 1.41 mequiv g−1 at 80 °C. This composite membrane also showed other promising properties such as good thermal and mechanical stability which exceeded the other composite membranes with different loading contents.
Co-reporter:Xiaogang Wang;Weilin Xu;Xiaochun Zhou
Journal of Solid State Electrochemistry 2009 Volume 13( Issue 9) pp:1449-1453
Publication Date(Web):2009 September
DOI:10.1007/s10008-008-0720-2
A prominent methanol-tolerant characteristic of the PtCeOx/C electrocatalyst was found during oxygen reduction reaction process. The carbon-supported platinum modified with cerium oxide (PtCeOx/C) as cathode electrocatalyst for direct methanol fuel cells was prepared via a simple and effective route. The synthesized electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. It was found that the cerium oxide within PtCeOx/C present in an amorphous form on the carbon support surface and the PtCeOx/C possesses almost similar disordered morphological structure and slightly smaller particle size compared with the unmodified Pt/C catalyst.
Co-reporter:Xiaochun Zhou, Yunjie Huang, Wei Xing, Changpeng Liu, Jianhui Liao and Tianhong Lu
Chemical Communications 2008 (Issue 30) pp:3540-3542
Publication Date(Web):29 May 2008
DOI:10.1039/B803661F
Pd–Au/C and Pd–Ag/C were found to have a unique characteristic of evolving high-quality hydrogen dramatically and steadily from the catalyzed decomposition of liquid formic acid at convenient temperature, and further this was improved by the addition of CeO2(H2O)x.
Co-reporter:Yuhan Lin, Haidong Li, Changpeng Liu, Wei Xing, Xiangling Ji
Journal of Power Sources 2008 Volume 185(Issue 2) pp:904-908
Publication Date(Web):1 December 2008
DOI:10.1016/j.jpowsour.2008.08.067
In this study, Nafion® 117 membrane is surface-modified with mesoporous silica layers through in situ surfactant-templated sol–gel reaction. The reaction makes use of tetraethyl orthosilicate (TEOS) under acidic condition via dip-coating technique on both sides. Scanning electron microscopy (SEM), Fourier transformation infrared (FTIR), and thermogravimetric analysis (TGA) are employed to characterize the resultant membranes. Proton conductivity and methanol permeability of the membranes are also studied. It is determined that the aging time, along with the number of the silicon dioxide (SiO2) layer, influence both proton conductivity and methanol permeability. Specifically, double-side modified membrane with 5 min interval of the second layer (S (5)) exhibits optimal properties on the combined criterion of conductivity and permeability. However, the application of mesoporous silica layer in modifying commercial Nafion membranes through dip-coating is proven to be a facile route in improving the said criteria simultaneously.
Co-reporter:Xiaochun Zhou, Changpeng Liu, Jianhui Liao, Tianhong Lu, Wei Xing
Journal of Power Sources 2008 Volume 179(Issue 2) pp:481-488
Publication Date(Web):1 May 2008
DOI:10.1016/j.jpowsour.2008.01.025
In this paper, it was found that the electrocatalytic activity of a Pt electrode for the electro-oxidation of formic acid could be dramatically enhanced with the modification of macrocycle compounds, such as iron-tetrasulfophthalocyanine (FeTSPc). The electro-oxidation of formic acid on a modified Pt electrode with FeTSPc occurs mainly through a direct pathway. A series of macrocycle compounds were also investigated as modifiers and exhibited a promotion effect similar to the Pt electrode. Therefore, platinum-macrocycle co-catalysts can promote the electro-oxidation of formic acid through a highly effective route, and are potential catalyst materials for a direct formic acid fuel cell (DFAFC).
Co-reporter:Zhonghua Zhang, Xiaogang Wang, Zhiming Cui, Changpeng Liu, Tianhong Lu, Wei Xing
Journal of Power Sources 2008 Volume 185(Issue 2) pp:941-945
Publication Date(Web):1 December 2008
DOI:10.1016/j.jpowsour.2008.07.044
Pd nanoparticles supported on WO3/C hybrid material have been developed as the catalyst for the oxygen reduction reaction (ORR) in direct methanol fuel cells. The resultant Pd–WO3/C catalyst has an ORR activity comparable to the commercial Pt/C catalyst and a higher activity than the Pd/C catalyst prepared with the same method. Based on the physical and electrochemical characterizations, the improvement in the catalytic performance may be attributed to the small particle sizes and uniform dispersion of Pd on the WO3/C, the strong interaction between Pd and WO3 and the formation of hydrogen tungsten bronze which effectively promote the direct 4-electron pathway of the ORR at Pd.
Co-reporter:Tiezhu Fu, Zhiming Cui, Shuangling Zhong, Yuhua Shi, Chengji Zhao, Gang Zhang, Ke Shao, Hui Na, Wei Xing
Journal of Power Sources 2008 Volume 185(Issue 1) pp:32-39
Publication Date(Web):15 October 2008
DOI:10.1016/j.jpowsour.2008.07.004
A new type of sulfonated clay (clay-SO3H) was prepared by the ion exchange method with the sulfanilic acid as the surfactant agent. The grafted amount of sulfanilic acid in clay-SO3H was 51.8 mequiv. (100 g)−1, which was measured by thermogravimetric analysis (TGA). Sulfonated poly(ether ether ketone) (SPEEK)/clay-SO3H hybrid membranes which composed of SPEEK and different weight contents of clay-SO3H, were prepared by a solution casting and evaporation method. For comparison, the SPEEK/clay hybrid membranes were produced with the same method. The performances of hybrid membranes for direct methanol fuel cells (DMFCs) in terms of mechanical and thermal properties, water uptake, water retention, methanol permeability and proton conductivity were investigated. The mechanical and thermal properties of the SPEEK membranes had been improved by introduction of clay and clay-SO3H, obviously. The water desorption coefficients of the SPEEK and hybrid membranes were studied at 80 °C. The results showed that the addition of the inorganic part into SPEEK membrane enhanced the water retention of the membrane. Both methanol permeability and proton conductivity of the hybrid membranes decreased in comparison to the pristine SPEEK membrane. However, it was worth noting that higher selectivity defined as ratio of proton conductivity to methanol permeability of the SPEEK/clay-SO3H-1 hybrid membrane with 1 wt.% clay-SO3H was obtained than that of the pristine SPEEK membrane. These results showed that the SPEEK/clay-SO3H hybrid membrane with 1 wt.% clay-SO3H had potential usage of a proton exchange membrane (PEM) for DMFCs.
Co-reporter:Zhonghua Zhang, Yunjie Huang, Junjie Ge, Changpeng Liu, Tianhong Lu, Wei Xing
Electrochemistry Communications 2008 Volume 10(Issue 8) pp:1113-1116
Publication Date(Web):August 2008
DOI:10.1016/j.elecom.2008.05.028
The hybrid material based on WO3 and Vulcan XC-72R carbon has been used as the support of Pd nanocatalysts. The resultant Pd–WO3/C catalysts in a large range of WO3 content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on the WO3/C support and the hydrogen spillover effect which greatly accelerates the dehydrogenation of HCOOH on Pd.
Co-reporter:Tiezhu Fu, Jing Wang, Jing Ni, Zhiming Cui, Shuangling Zhong, Chengji Zhao, Hui Na, Wei Xing
Solid State Ionics 2008 Volume 179(Issue 39) pp:2265-2273
Publication Date(Web):15 December 2008
DOI:10.1016/j.ssi.2008.08.009
Sulfonated poly(ether ether ketone) (SPEEK) and aminopropyltriethoxysilane (KH550) hybrid membranes doped with different weight ratio of phosphotungstic acid (PWA) were prepared by the casting procedure, as well as PWA as a catalyst for sol–gel process of KH550. The chemical structures of hybrid membranes were characterized by energy dispersive X-ray spectrometry (EDX) and Fourier transform infrared spectroscopy (FTIR). The morphology of hybrid membranes was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results had proved the uniform and homogeneous distribution of KH550 and PWA in these hybrid membranes. The influence of the dispersed PWA on the properties of membranes such as thermal stability, water uptake, swelling ratio, and proton conductivity was researched. Thermogravimetry analysis (TGA) results indicated that the hybrid membranes had high thermal stability below 200 °C. The dimensional stabilities of the hybrid membranes were improved by addition of KH550-10/PWA compared with the pristine SPEEK. The proton conductivity of the hybrid membrane with 5 wt.% PWA into SPEEK/KH550-10 reached the maximum of 0.084 S cm− 1 at 25 °C and 0.16 S cm− 1 at 80 °C under the 100% relative humidity condition. The proton conductivity mechanism in the hybrid membranes was discussed. Therefore, the possibility of the hybrid membranes for usage in proton exchange membrane fuel cells (PEMFCs) was explored.
Co-reporter:Junjie Ge, Yuwei Zhang, Changpeng Liu, Tianhong Lu, Jianhui Liao and Wei Xing
The Journal of Physical Chemistry C 2008 Volume 112(Issue 44) pp:17214-17218
Publication Date(Web):2017-2-22
DOI:10.1021/jp8057965
In this paper, a simple chemical reduction route is discussed that results in small size, uniform dispersion of Pd nanoparticles supported on carbon black. HVO42−, the tridentate oxoanion with its O−O distance of 2.76 Å, closely matching with the Pd−Pd distance (2.75 Å), is expected to be an effective stabilizer for Pd according to the lattice size-matching binding model (Finke, R. G.; Özkar, S. Coord. Chem. Rev. 2004, 248, 135). Because it has never been tested, HVO42− is exploited and found to be a very simple and effective stabilizer. TEM shows the formation of dispersed Pd nanoparticles supported on carbon with an average particle size of 4.8 nm and rather narrow size distribution. Adsorbed HVO42− can be completely removed after Pd reduction by simply washing with water, as indicated by EDX measurement. The Pd/C catalyst thus prepared shows greatly enhanced activities for the HCOOH electrooxidation reaction compared to catalyst commonly reduced by NaBH4 due to the size reduction of Pd and the uniform distribution. The chemical reduction route of Pd/C catalyst with HVO42− as stabilizer is very simple and has great potentials for mass-producing Pd/C and others noble metal catalysts.
Co-reporter:Zhiming Cui, Nanwen Li, Xiaochun Zhou, Changpeng Liu, Jianhui Liao, Suobo Zhang, Wei Xing
Journal of Power Sources 2007 Volume 173(Issue 1) pp:162-165
Publication Date(Web):8 November 2007
DOI:10.1016/j.jpowsour.2007.08.006
Surface-modified Nafion® membrane was prepared by casting proton-conducting polyelectrolyte complexes on the surface of Nafion®. The casting layer is homogeneous and its thickness is about 900 nm. The proton conductivity of modified Nafion® is slightly lower than that of plain Nafion®; however, its methanol permeability is 41% lower than that of plain Nafion®. The single cells with modified Nafion® exhibit higher open circuit voltage (OCV = 0.73 V) and maximal power density (Pmax = 58 mW cm−2) than the single cells with plain Nafion® (OCV = 0.67 V, Pmax = 49 mW cm−2). It is a simple, efficient, cost-effective approach to modifying Nafion® by casting proton-conducting materials on the surface of Nafion®.
Co-reporter:Zhiming Cui, Changpeng Liu, Tianhong Lu, Wei Xing
Journal of Power Sources 2007 Volume 167(Issue 1) pp:94-99
Publication Date(Web):1 May 2007
DOI:10.1016/j.jpowsour.2006.12.112
Polyelectrolyte complexes (PECs) of chitosan and phosphotungstic acid have been prepared and evaluated as novel proton-conducting membranes for direct methanol fuel cells. Phosphotungstic acid can be fixed within PECs membranes through strong electrostatic interactions, which avoids the decrease of conductivity caused by the dissolving of phosphotungstic acid as previously reported. Scanning electron microscopy (SEM) shows that the PECs membranes are homogeneous and dense. Fourier transform infrared spectroscopy (FTIR) demonstrates that hydrogen bonding is formed between chitosan and phosphotungstic acid. Thermogravimetric analysis (TGA) shows that the PECs membranes have good thermal stability up to 210 °C. The PECs membranes exhibit good swelling properties and low methanol permeability (P, 3.3 × 10−7 cm2 s−1). Proton conductivity (σ) of the PECs membranes increases at elevated temperature, reaching the value of 0.024 S cm−1 at 80 °C.
Co-reporter:Tian Tian, Changpeng Liu, Jianhui Liao, Wei Xing, Tianhong Lu
Journal of Power Sources 2007 Volume 174(Issue 1) pp:176-179
Publication Date(Web):22 November 2007
DOI:10.1016/j.jpowsour.2007.08.082
It is reported for the first time that the slow electrochemical kinetics process for the electro-oxidation of ethanol can be promoted by changing the electrochemical environment. The electro-oxidation of ethanol at a Pt electrode in the presence of Eu3+ cations was studied and an enhancement effect was exhibited. Cyclic voltammetry experiment results showed that the peak current density for the electro-oxidation of ethanol was increased in the presence of Eu3+ in the ethanol solution. A preliminary discussion of the mechanism of the enhancement effect is given. This is based on a CO stripping experiment, which shows that either the onset potential or the peak potential of CO oxidation is shifted negatively after adding Eu3+ to the solution.
Co-reporter:Xinzhong Xue, Junjie Ge, Tian Tian, Changpeng Liu, Wei Xing, Tianhong Lu
Journal of Power Sources 2007 Volume 172(Issue 2) pp:560-569
Publication Date(Web):25 October 2007
DOI:10.1016/j.jpowsour.2007.05.091
In this paper, five Pt3Sn1/C catalysts have been prepared using three different methods. It was found that phosphorus deposited on the surface of carbon with Pt and Sn when sodium hypophosphite was used as reducing agent by optimization of synthetic conditions such as pH in the synthetic solution and temperature. The deposition of phosphorus should be effective on the size reduction and markedly reduces PtSn nanoparticle size, and raise electrochemical active surface (EAS) area of catalyst and improve the catalytic performance. TEM images show PtSnP nanoparticles are highly dispersed on the carbon surface with average diameters of 2 nm. The optimum composition is Pt3Sn1P2/C (note PtSn/C-3) catalyst in my work. With this composition, it shows very high activity for the electrooxidation of ethanol and exhibit enhanced performance compared with other two Pt3Sn1/C catalysts that prepared using ethylene glycol reduction method (note PtSn/C-EG) and borohydride reduction method (note PtSn/-B). The maximum power densities of direct ethanol fuel cell (DEFC) were 61 mW cm−2 that is 150 and 170% higher than that of the PtSn/C-EG and PtSn/C-B catalyst.
Co-reporter:Lin Zhu;DongMei Sun;TianHong Lu;ChenXin Cai
Science China Chemistry 2007 Volume 50( Issue 3) pp:304-307
Publication Date(Web):2007 June
DOI:10.1007/s11426-007-0078-9
A newfangled direct electrochemistry behavior of Cytochrome c (Cyt c) was found on glassy carbon (GC) electrode modified with the silicon dioxide (SiO2) nanoparticles by physical adsorption. A pair of stable and well-defined redox peaks of Cyt c′ quasi-reversible electrochemical reaction were obtained with a heterogeneous electron transfer rate constant of 1.66×10−3 cm/s and a formal potential of 0.069 V (vs. Ag/AgCl) (0.263 V versus NHE) in 0.1 mol/L pH 6.8 PBS. Both the size and the amount of SiO2 nanoparticles could influence the electron transfer between Cyt c and the electrode. Electrostatic interaction which is between the negative nanoparticle surface and positively charged amino acid residues on the Cyt c surface is of importance for the stability and reproducibility toward the direct electron transfer of Cyt c. It is suggested that the modification of SiO2 nanoparticles proposes a novel approach to realize the direct electrochemistry of proteins.
Co-reporter:Changpeng Liu, Xinzhong Xue, Tianhong Lu, Wei Xing
Journal of Power Sources 2006 Volume 161(Issue 1) pp:68-73
Publication Date(Web):20 October 2006
DOI:10.1016/j.jpowsour.2006.03.084
It is suggested that a Pt/C cathodic catalyst for the direct methanol fuel cell (DMFC) can be prepared with a pre-precipitation method, in which, H2PtCl6 is precipitated onto the carbon black as (NH4)2PtCl6 before H2PtCl6 is reduced to Pt. The electrocatalytic activity of this Pt/C-A catalyst for oxygen reduction is excellent because the Pt/C catalyst prepared with this pre-precipitation method possesses a small average particle size, low relative crystalinity and a large electrochemically active surface area. In addition, the pre-precipitation method is simple and economical and it can be used to prepare a Pt/C catalyst on a large scale.
Co-reporter:Xinzhong Xue, Junjie Ge, Changpeng Liu, Wei Xing, Tianhong Lu
Electrochemistry Communications 2006 Volume 8(Issue 8) pp:1280-1286
Publication Date(Web):August 2006
DOI:10.1016/j.elecom.2006.06.010
A novel method was developed to prepare the highly active Pt–Ru–P/C catalyst. The deposition of phosphorus significantly increased electrochemical active surface (EAS) area of catalyst by reduces Pt–Ru particle size. TEM images show that Pt–Ru–P nanoparticles have an uniform size distribution with an average diameter of 2 nm. Cyclic voltammetry (CV), Chronoamperometry (CA), and CO stripping indicate that the presence of non-metal phosphorus as an interstitial species Pt–Ru–P/C catalyst shows high activity for the electro-oxidation of methanol, and exhibit enhanced performance in the oxidation of carbon monoxide compared with Pt–Ru/C catalyst. At 30 °C and pure oxygen was fed to the cathode, the maximum power density of direct methanol fuel cell (DMFC) with Pt–Ru–P/C and Pt–Ru/C catalysts as anode catalysts was 61.5 mW cm−2 and 36.6 mW cm−2, respectively. All experimental results indicate that Pt–Ru–P/C catalyst was the optimum anode catalyst for direct methanol fuel cell.
Co-reporter:Xiaochun Zhou, Songtao Li, Yi Su, Changpeng Liu, Mingyou Huang, Tianhong Lu, Wei Xing
Journal of Electroanalytical Chemistry 2006 Volume 588(Issue 1) pp:129-139
Publication Date(Web):1 March 2006
DOI:10.1016/j.jelechem.2005.12.013
An additional anode catalyst layer with PtRu/C was hot pressed between two Nafion® 112 membranes and a conventional direct methanol fuel cell (DMFC) cathode/membrane/anode assembly with the above membranes as separator was fabricated. The additional catalyst layer formed an assistant cell with the cathode to prevent methanol crossover. A simple one-dimensional mathematical model was presented to describe the performance of this new type of membrane electrode assembly system. As seen from both experimental result and model analysis, the additional catalyst layer can not only effectively prevent the methanol crossover, but also generate electrical power with the crossover methanol. The percentage of output power of the assistant cell to the total power analyzed by the model is about 40% under usual condition, which is much higher than that from experimental result, indicating the potential of the development in the DMFC designing. It was also discovered that the electrical power generated from the assistant cell with crossover methanol could take higher percentage in total electrical power when the main DMFC current density became lower.
Co-reporter:Xinzhong Xue, Tianhong Lu, Changpeng Liu and Wei Xing
Chemical Communications 2005 (Issue 12) pp:1601-1603
Publication Date(Web):27 Jan 2005
DOI:10.1039/B418227H
A carbon supported Pt–Ru catalyst with uniform distribution and small average size of the Pt–Ru particles was synthesized using a two-step spray pyrolysis (SP) method; the electrocatalytic activity of the prepared catalyst for methanol oxidation is better than that of the standard commercial catalyst.
Co-reporter:Weilin Xu, Tianhong Lu, Changpeng Liu, Wei Xing
Electrochimica Acta 2005 Volume 50(16–17) pp:3280-3285
Publication Date(Web):30 May 2005
DOI:10.1016/j.electacta.2004.12.014
Nafion/silica/phosphotungstic acid (PWA) composite membranes were studied for low temperature (<100 °C) direct methanol fuel cells (DMFCs). The composite membranes were prepared by sol–gel reaction of tetraethoxysilane (TEOS) within the nanophase of hydrated perfluorosulfonic acid membranes (Nafion 117) and the subsequent treatment in phosphotungstic acid (PWA) solution. X-ray diffraction (XRD) indicates that the silica can decrease the crystallinity of Nafion. The silica in membranes can greatly decrease the methanol diffusion coefficient (D) within appropriate silica content range. The proton conductivities (σ) of these composite membranes are higher than those of commercial Nafion 117. The result of σ/D shows the optimal silica content in composite membrane is 38.2 μg/g. Thermogravimetric analysis (TGA) shows that the incorporation of silica and PWA does not affect the thermostability of membrane. The data from single direct methanol fuel cell using these two membranes of commercial Nafion without treatment and Nafion/silica/PWA composite membranes with optimal silica content as polymer–electrolyte show that the cell with composite membrane has higher open circuit voltage (OCV = 0.75 V) and maximal power density (Pmax = 70 mW/cm2) than those of commercial Nafion without treatment (OCV = 0.68 V, Pmax = 62 mW/cm2) at 80 °C.
Co-reporter:Xinzhong Xue, Tianhong Lu, Changpeng Liu, Weilin Xu, Yi Su, Yanzhuo Lv, Wei Xing
Electrochimica Acta 2005 Volume 50(16–17) pp:3470-3478
Publication Date(Web):30 May 2005
DOI:10.1016/j.electacta.2004.12.034
It is reported for the first time that Pt–Ru/C catalysts were prepared in the ionic liquids. This novel preparation method has some advantages, such as the high electrocatalytic activity of the catalysts for the methanol oxidation, simple preparation procedure, recycle of the ionic liquids, etc. In the best preparation conditions, the electrocatalytic activity of the Pt–Ru/C catalyst prepared in the ionic liquid for methanol oxidation is higher than that of the commercial E-Tek Pt–Ru/C catalyst. It is mainly due to the low crystallinity of the Pt–Ru particles and the abundant Ru oxides on the surface of the Pt–Ru/C catalysts. Therefore, this kind of preparation method of the catalysts has potential applications for the direct methanol fuel cell (DMFC).
Co-reporter:Lin Zhu, Kunqi Wang, Tianhong Lu, Wei Xing, Jing Li, Xiangguang Yang
Journal of Molecular Catalysis B: Enzymatic (September 2008) Volume 55(Issues 1–2) pp:93-98
Publication Date(Web):1 September 2008
DOI:10.1016/j.molcatb.2008.01.013
It is discovered that SBA-15 (santa barbara amorphous) can provide the favorable microenvironments and optimal direct electron-transfer tunnels (DETT) of immobilizing cytochrome c (Cyt c) by the preferred orientation on it. A high-redox potential (254 mV vs. Ag/AgCl) was obtained on glassy carbon (GC) electrode modified by immobilizing Cyt c on rod-like SBA-15. With ultraviolet–visible (UV–vis), circular dichroism (CD), FTIR and cyclic voltammetry, it was demonstrated that immobilization made Cyt c exhibits stable and ideal electrochemical characteristics while the biological activity of immobilized Cyt c is retained as usual. The electrochemistry behavior at the modified GC electrode is surface-controlled quasi-reversible process with an enhanced electron-transfer rate constant of 2.20 s−1 because of the optimal DETT between Cyt c and SBA-15. It was also found that the modified GC electrode exhibited a predominant electrocatalytic activity for the reduction of hydrogen peroxide, which may open up a possibility for designing and fabricating enzyme electrodes with application potentials in biosensor and biofuel cells.
Co-reporter:Kunqi Wang, Hua Yang, Lin Zhu, Jianhui Liao, Tianhong Lu, Wei Xing, Shenyang Xing, Qiang Lv
Journal of Molecular Catalysis B: Enzymatic (June 2009) Volume 58(Issues 1–4) pp:194-198
Publication Date(Web):1 June 2009
DOI:10.1016/j.molcatb.2008.12.022
In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified by ordered mesoporous silica-SBA-15 and Nafion. The sorption behavior of GOD immobilized on SBA-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet–visible (UV–vis), FTIR, respectively, which demonstrated that SBA-15 can facilitate the electron exchange between the electroactive center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and SBA-15 matrices displays direct, nearly reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 3.89 s−1 in 0.1 M phosphate buffer solution (PBS) (pH 7.12). Furthermore, it was also discovered that, in the absence of O2, GOD immobilized on Nafion and SBA-15 matrices can produce a wide linear response to glucose in the positive potential range. Thus, Nafion/GOD-SBA-15/GC electrode is hopeful to be used in the third non-mediator's glucose biosensor. In addition, GOD immobilized on SBA-15 and Nafion matrices possesses an excellent bioelectrocatalytic activity for the reduction of O2. The Nafion/GOD-SBA-15/GC electrode can be utilized as the cathode in biofuel cell.
Co-reporter:Ligang Feng, Fengzhan Si, Shikui Yao, Weiwei Cai, Wei Xing, Changpeng Liu
Catalysis Communications (31 March 2011) Volume 12(Issue 8) pp:772-775
Publication Date(Web):31 March 2011
DOI:10.1016/j.catcom.2011.01.012
PtPd/C catalysts with different surface compositions (Pt + Pd, Pt–Pd and Pd–Pt) were synthesized with different deposition sequences, and characterized by electrochemical experiments and XPS measurements. The different catalytic characteristics for formic acid electrooxidation occurred on the three PtPd/C catalysts were preliminarily discussed according to the oxidation pathway. Due to the synergistic effect between Pt and Pd, especially for Pt + Pd, the catalytic stability for formic acid oxidation was greatly increased. The results are helpful in preparing of PtPd catalyst and understanding the oxidation mechanism for formic acid oxidation.Download full-size imageResearch Highlights► PtPd/C catalysts with different surface compositions are successfully synthesized. ► Catalytic characteristics for FAEO are discussed on the different PtPd/C catalysts. ► Surprised current oscillation phenomenons occur on the Pt–Pd catalyst. ► Combination of Pt and Pd can increase the catalytic activity stability for FAEO.
Co-reporter:Liang Yan, Shikui Yao, Jinfa Chang, Changpeng Liu, Wei Xing
Journal of Power Sources (15 March 2014) Volume 250() pp:128-133
Publication Date(Web):15 March 2014
DOI:10.1016/j.jpowsour.2013.10.085
Co-reporter:Xiao Zhao, Jianbing Zhu, Liang Liang, Jianhui Liao, Changpeng Liu and Wei Xing
Journal of Materials Chemistry A 2012 - vol. 22(Issue 37) pp:NaN19725-19725
Publication Date(Web):2012/08/03
DOI:10.1039/C2JM33926A
The development of advanced support materials displays the potential for both reducing the cost and simultaneously increasing the activity of catalysts. In the current work, a novel N-doped carbon coated hydrophilic titanium dioxide (TiO2@N-doped C) nano-composite, constructed by the procedure of an in situ polymerization and subsequent pyrolysis, was utilized to support Pt nano-crystals for the methanol oxidation reaction (MOR). The as-prepared Pt/TiO2@N-doped C catalyst generated 1.74-fold higher activity, 2.08-fold higher stability and much better resistance to CO poisoning than a commercial state-of-the-art Pt/C catalyst. The enhanced catalytic performance was ascribed to the improved CO tolerance and the catalyst–support interaction due to the utilization of the TiO2@N-doped C nano-composite, which not only provides rich active –OH groups to promote CO oxidation via the bifunctional mechanism, but also modifies the electronic structure of the Pt NPs to improve the intrinsic kinetics of MOR. The as-developed TiO2@N-doped C nano-composite is a highly promising catalyst support material for use in fuel cell technology.
Co-reporter:Jianbing Zhu, Meiling Xiao, Xiao Zhao, Kui Li, Changpeng Liu and Wei Xing
Chemical Communications 2014 - vol. 50(Issue 81) pp:NaN12203-12203
Publication Date(Web):2014/08/14
DOI:10.1039/C4CC04887C
A novel nitrogen doped carbon–graphene support for a direct methanol fuel cell was synthesised via thermal decomposition of the graphene oxide–polypyrrole composite. The supported catalysts show considerable enhancement of activity and stability towards the methanol electro-oxidation reaction. Physical characterizations reveal that the enhanced performance was due to a uniform particle dispersion and modified electronic structure of platinum nanoparticles by the support.
Co-reporter:Jianbing Zhu, Meiling Xiao, Kui Li, Changpeng Liu and Wei Xing
Chemical Communications 2015 - vol. 51(Issue 15) pp:NaN3218-3218
Publication Date(Web):2015/01/13
DOI:10.1039/C4CC09528F
A novel PtFe@Pt core–shell nanostructure with a PtFe bimetallic core and a nanodendrite Pt shell was fabricated through a facile aqueous reduction process. Without any capping agent and/or surfactant, a clean Pt surface can be obtained. The novel nanostrutured crystals show superior electrocatalytic performance towards methanol oxidation due to the enlarged Pt surface area and the modified electronic structure of Pt.
Co-reporter:Min Yin, Yunjie Huang, Liang Liang, Jianhui Liao, Changpeng Liu and Wei Xing
Chemical Communications 2011 - vol. 47(Issue 28) pp:NaN8174-8174
Publication Date(Web):2011/06/20
DOI:10.1039/C1CC12561C
CO poisoning during methanol electrooxidation was investigated on PtAu alloys with different surface compositions. Results show that the CO formation can be reduced gradually with increasing surface Au fractions in PtAu alloys and CO poisoning can be almost eliminated by adjusting to a proper surface Au fraction.
Co-reporter:Ligang Feng, Xiujuan Sun, Changpeng Liu and Wei Xing
Chemical Communications 2012 - vol. 48(Issue 3) pp:NaN421-421
Publication Date(Web):2011/10/26
DOI:10.1039/C1CC16522D
A surprisingly high and stable current was observed after the peak current on the PdHoOx/C catalyst indicating the diminished poisoning effect. Moreover, the novel PdHoOx/C catalyst exhibited excellent catalytic activity and stability for formic acid oxidation due to the large electrochemical surface area and electronic effect.
Co-reporter:Yuwei Zhang, Weiwei Cai, Fengzhan Si, Junjie Ge, Liang Liang, Changpeng Liu and Wei Xing
Chemical Communications 2012 - vol. 48(Issue 23) pp:NaN2872-2872
Publication Date(Web):2012/01/20
DOI:10.1039/C2CC17230E
We developed a method to significantly decrease the methanol permeability of a Nafion membrane that does not require sacrificing its proton conductivity and mechanical stability. The Nafion membrane modified by the coating of a thin layer of sulfonated organic silica on the membrane surface exhibits significantly decreased methanol permeability—the permeability is decreased to an undetectable level—while retaining an acceptable ionic conductivity of 0.029 S cm−1.
Co-reporter:Xiaochun Zhou, Yunjie Huang, Wei Xing, Changpeng Liu, Jianhui Liao and Tianhong Lu
Chemical Communications 2008(Issue 30) pp:NaN3542-3542
Publication Date(Web):2008/05/29
DOI:10.1039/B803661F
Pd–Au/C and Pd–Ag/C were found to have a unique characteristic of evolving high-quality hydrogen dramatically and steadily from the catalyzed decomposition of liquid formic acid at convenient temperature, and further this was improved by the addition of CeO2(H2O)x.
Co-reporter:Jianbing Zhu, Meiling Xiao, Changpeng Liu, Junjie Ge, Jean St-Pierre and Wei Xing
Journal of Materials Chemistry A 2015 - vol. 3(Issue 43) pp:NaN21459-21459
Publication Date(Web):2015/09/09
DOI:10.1039/C5TA06181D
Non-platinum (NP) electrocatalysts with high activity and durability for oxygen reduction reactions (ORR) are required for fuel cells and other renewable systems. To avoid trial-and-error methods and achieve the rational design and synthesis of efficient NP catalysts, in-depth knowledge of the formation/growth mechanism of nanocatalysts and the origin of active sites is highly desirable. Here, we report a new class of NP catalysts with a novel structure of Fe3C encapsulated in N-doped carbon nanotubes/C. We study the formation mechanism of the nanostructure to pave the way for controlled fabrication of high-performance NP catalysts. The encapsulation of iron into carbon occurs during the first step of CNT growth and the surface functional groups on carbon black are identified as being essential for forming CNTs. The catalyst shows ultrahigh catalytic performance in both acid and alkaline media. We also examine the structure–performance dependency. The catalytic performance is highly dependent on the nanostructure and the encapsulation of Fe3C. Fe affects the catalytic performance through electronic effects rather than by directly participating in the active sites. This result is confirmed by DFT calculations, which show an increase in the density of states and a reduction in the local work function, XPS studies, and electrochemical measurements. The likelihood of N participating in the active sites is low because the catalytic performance does not depend on pyridinic and graphitic N.
Co-reporter:Yunjie Huang, Qingfeng Li, Annemette H. Jensen, Min Yin, Jens Oluf Jensen, Erik Christensen, Chao Pan, Niels J. Bjerrum and Wei Xing
Journal of Materials Chemistry A 2012 - vol. 22(Issue 42) pp:NaN22458-22458
Publication Date(Web):2012/08/31
DOI:10.1039/C2JM34704K
A new proton conductor based on niobium phosphates was synthesized using niobium pentoxide and phosphoric acid as precursors. The existence of hydroxyl groups in the phosphates was confirmed and found to be preserved after heat treatment at 500 °C or higher, contributing to an anhydrous proton conductivity of 1.6 × 10−2 S cm−1 at 250 °C. The conductivity increased with water content in the atmosphere and reached 5.8 × 10−2 S cm−1 under pure water vapour at the same temperature. The conductivity showed good stability in the low water partial pressure range of up to 0.05 atm. The metal phosphates are of high interest as potential proton conducting electrolytes for fuel cells operational in an intermediate temperature range.
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