Co-reporter:Muhammad Tahir, Lun Pan, Rongrong Zhang, Yi-Cheng Wang, Guoqiang Shen, Imran Aslam, M. A. Qadeer, Nasir Mahmood, Wei Xu, Li Wang, Xiangwen Zhang, and Ji-Jun Zou
ACS Energy Letters September 8, 2017 Volume 2(Issue 9) pp:2177-2177
Publication Date(Web):August 28, 2017
DOI:10.1021/acsenergylett.7b00691
The electrocatalytic oxygen evolution reaction (OER) plays a critical role in sustainable energy conversion and storage, but OER is severely hampered owing to the lack of highly efficient catalysts. Here, we report an efficient electrocatalyst, with NiO/Co3O4 nanoparticles decorated on nitrogen-doped carbon (NiO/Co3O4@NC). Abundant high-valence Ni3+ and Co3+ species were observed on the surface of the hybrid due to the strong NC–metal oxide and NiO–Co3O4 interactions. This unique structure leads to excellent OER performance, delivering a very low overpotential of 240 mV@10 mA·cm–2 on glassy carbon and 200 mV@10 mA·cm–2 on Ni foam in KOH and having a turnover frequency (@350 mV overpotential) 6 and 16 times higher than that of IrO2 and RuO2, respectively.
Co-reporter:Xiu-tian-feng E;Yu Zhang;Xiangwen Zhang;Li Wang
Industrial & Engineering Chemistry Research August 6, 2014 Volume 53(Issue 31) pp:12312-12318
Publication Date(Web):2017-2-22
DOI:10.1021/ie502311x
Catalytic cracking of hydrocarbon fuels is an effective way to cool aircraft materials under hypersonic flight. Pseudohomogeneous catalysis is an alternative to overcome the problems of traditional catalyst coatings. Herein, we employed the Brust–Schiffrin method to synthesize Pt and Pd nanoparticles (NPs) using oleylamine as the protecting ligand. The particle size can be controlled by tuning the ratio of protecting ligand, and uniform NPs can be obtained at an oleylamine/NP molar ratio of 2, with Pt and Pd NPs of 1–3 and 2–5 nm, respectively. IR and TG characterizations confirmed that the amine group of oleylamine is chelated on the metal surface whereas the hydrophobic carbon chain is exposed in the hydrocarbon fuel. As a result, the NPs are highly dispersible in jet fuel JP-10 without any precipitation after standing 12 months, providing the possibility of pseudohomogeneous catalysis. Suspensions containing Pt and Pd NPs (50 ppm) exhibited markedly enhanced cracking performance, with cracking conversions, gas yields, and heat sinks at 680 °C that were, respectively, 4.5, 4.4, and 1.3 and 3.1, 3.6, and 1.2 times of pure JP-10. In particular, Pt NPs can reduce the onset temperature of the cracking reaction from 650 to 600 °C. This work demonstrates the potential of fuel-dispersible NPs in hypersonic applications.
Co-reporter:Zhen-Feng Huang, Jiajia Song, Xin Wang, Lun Pan, Ke Li, Xiangwen Zhang, Li Wang, Ji-Jun Zou
Nano Energy 2017 Volume 40(Volume 40) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.nanoen.2017.08.032
•Inherent driving force for Z-scheme charge transfer at semiconductor-semiconductor interface is demonstrated.•Type-II charge transfer pathway for C3N4/W18O49 is switched to Z-scheme by modulating interfacial band bending.•Z-scheme C3N4/W18O49 exhibits H2 evolution rate of 8597 μmol h−1 g−1.•High AQY of 39.1% at 420 nm is obtained.Z-scheme composite represents an ideal system for photocatalytic hydrogen evolution, but the charge transfer mechanism is still ambiguous, and how to design and construct such system is a big challenge. Herein, we demonstrate that C3N4-W18O49, the type-II composite, can be switched to direct Z-scheme via modulating the interfacial band bending. Experiment and DFT computation results reveal that the adsorption of triethanolamine (TEOA) on C3N4 surface significantly uplifts its Femi level, inverses the continuous interfacial band bending to interrupted one, and thus switches the composite from type-II to Z-scheme, without the assistance of any electron shuttles. Importantly, this Z-scheme C3N4/W18O49 composites exhibit much better photocatalytic H2 activity compared with pure C3N4, and obtain H2 evolution rate of 8597 μmol h−1 g−1 (AQY of 39.1% at 420 nm) with Pt as cocatalyst and TEOA as hole scavenger. Also, using this hypothesis we successfully explain why C3N4/WO3 is inherent Z-scheme composite but the performance is not as good as C3N4/W18O49 and why TEOA is the best hole scavenger for C3N4. This work is expected to give deep insights into understanding the charge transfer in semiconductor composites and rationally designing and constructing Z-scheme photocatalyst for hydrogen evolution.The adsorption of triethylamine (TEOA) on C3N4 surface significantly uplifts its Femi level, inverses the continuous interfacial band bending to interrupted one, and thus switches the composite from type-II to Z-scheme, without the assistance of any electron shuttles. C3N4/W18O49 composites exhibit much better photocatalytic H2 activity compared with pure C3N4, and obtain H2 evolution rate of 8597 μmol h−1 g−1 (AQY of 39.1% at 420 nm) with Pt as cocatalyst and TEOA as hole scavenger.Download high-res image (130KB)Download full-size image
Journal of Energy Chemistry 2017 Volume 26, Issue 6(Volume 26, Issue 6) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.jechem.2017.07.021
Noble-metal-free hydrogen/oxygen evolution reaction (HER/OER) electrocatalysts, especially bifunctional electrocatalysts, are essential for overall water splitting, but their performance is impeded by many factors like poor electrical conductivity. Herein, we fabricated cobalt phosphide (CoP) nanoparticles embedded in P and N co-doped carbon (PNC) matrix (CoP@PNC) to fully realize the high activity of CoP by maximizing its conductivity. Simply a carbonization coupled phosphidation approach was utilized where Co ions and organic ligands of Co-MOF were transferred into CoP and P and N co-doped carbon. The synthesized material shows an ideal electrical conductivity, excellent HER (overpotential of −84 mV and −120 mV @10 mA cm−2 in acidic and alkaline medias, respectively) and OER (overpotential of 330 mV@10 mA cm−2 in alkaline media) performances. Further, CoP@PNC acts as a superior catalyst for both anode and cathode to catalyze overall water splitting and only requires an voltage of 1.52 V to deliver a current density of 10 mA cm−2, superior to the noble-metal catalysts system (Pt/C//IrO2) and the reported noble-metal-free bifunctional electrocatalysts.CoP nanoparticles fully embedded in P and N co-doped carbon matrix (CoP@PNC) show excellent overall water splitting activity superior to the state-of-the-art Pt/C//IrO2 and other reported bifunctional catalysts.Download high-res image (138KB)Download full-size image.
Co-reporter:Muhammad Tahir, Lun Pan, Faryal Idrees, Xiangwen Zhang, Li Wang, Ji-Jun Zou, Zhong Lin Wang
Nano Energy 2017 Volume 37(Volume 37) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.nanoen.2017.05.022
•The recent efforts in water oxidation electrocatalysis were reviewed.•The standard parameters to evaluate the performance were emphasized.•This review also provides the future direction and application.Water oxidation or oxygen evolution reaction (OER) electrocatalysis got much attention in the last few years because of its prime role in water splitting, rechargeable metal-air batteries and fuel cells. Therefore, the development of efficient, abundant and economical catalysts for water oxidation reaction is one of the main subjects of present study in renewable energies. This review article summarizes the very recent efforts in the field of OER electrocatalysis along with the faced challenges. The solutions to these challenges also outline with appropriate examples of scientific literatures. Significantly, the present review will provide the standards to evaluate the activity and stability for heterogeneous OER catalysts. It will clearly summarize the future directions and applications, especially the combination of sustainable energy utilization (like triboelectric nanogenerator) with water splitting. The providing study will help to explore and develop better catalysts and units for practical applications and will offer basic understanding of OER process along with the standard parameters to evaluate the performance.Download high-res image (149KB)Download full-size image
•Biofuel with density of 0.804 g/cm3 and freezing point lower than − 80 °C•Lignin-derived anisole/guaiacol/phenol and hemicellulose/cellulose-derived furfural alcohol as feedstock•Biofuel synthesized by simple alkylation and hydrodeoxygenation•A semi-continuous operation adopted to improve the conversion while keep the selectivityConverting chemicals that can be derived from lignocellulose to cyclic hydrocarbons is a promising route for the synthesis of high-density biofuels. But the low-temperature properties of most synthesized fuels are not good, with high viscosity and freezing point. Herein, we presented the synthesis of cyclohexane derivatives by the alkylation of aromatic oxygenates (anisole, guaiacol and phenol) with furfural alcohol (furfuryl alcohol and 5-hydroxymethylfurfural), followed with hydrodeoxygenation. It is found that FeCl3 exhibits relatively high activity and selectivity for the alkylation of anisole (guaiacol), and AlCl3 is the best catalyst for phenol. The selectivity of mono-alkylation product is 71.0%, 92.4% and 84.3% for the alkylation of anisole, guaiacol and phenol with furfuryl alcohol when the reactant ratio is 10, respectively. A semi-continuous operation was adopted for the alkylation of furfuryl alcohol to improve the conversion of aromatic oxygenates. When furfuryl alcohol is replaced by 5-hydroxymethylfurfural, the selectivity reaches almost 100%, but the reaction is a little slower and longer time is needed to get full conversion. After hydrodeoxygenation by combination of Pd/C and HZSM-5, the alkylation product was converted to branched cyclohexane with density of 0.804 g/cm3 at 20 °C, kinematic viscosity of 34.4 mm2/s at − 60 °C and freezing point lower than − 80 °C, which shows great potential as additive to promote the low-temperature properties of other fuels.
Journal of Materials Chemistry A 2017 vol. 5(Issue 39) pp:20932-20937
Publication Date(Web):2017/10/10
DOI:10.1039/C7TA06981B
Well-dispersed and highly efficient molybdenum nitrides on a nitrogen-doped carbon matrix (Mo2N@NC) are reported as a new and active electrocatalyst for hydrogen evolution in alkaline electrolyte. The key point in fabricating this catalyst is using HNO3-treated melamine, other than pristine melamine, as carbon and nitrogen pools to realize the complete nitridation of MoO3 to Mo2N nanoparticles of 4 nm size and at the same time to generate a nitrogen-doped carbon matrix to support these nanoparticles by thermolysis under an Ar atmosphere. The as-prepared Mo2N@NC exhibits excellent HER activity in 1 M KOH with a pretty low overpotential of 85 mV to achieve a current density of 10 mA cm−2 and a small Tafel slope of 54 mV dec−1, which is among the best for Mo-based compounds and better than those of most non-noble metal electrocatalysts to date in alkaline media. It is also much better than those of the incomplete nitride compounds (MoO2/Mo2N@NC) and the mixture of nitrides and carbides (Mo2N/Mo2C@NC) fabricated under similar conditions, from aspects of overpotential, Tafel slope, exchange current density, conductivity, active surface area and turnover frequencies. Therefore, Mo2N represents a new kind of very active HER catalyst in alkaline electrolyte. Also, this work provides an effective method to fabricate metal nitrides/carbon composites for other applications.
Co-reporter:Junjian Xie;Xiangwen Zhang;Lun Pan;Genkuo Nie;Xiu-Tian-Feng E;Qing Liu;Peng Wang;Yafei Li
Chemical Communications 2017 vol. 53(Issue 74) pp:10303-10305
Publication Date(Web):2017/09/14
DOI:10.1039/C7CC05101H
Renewable high-density spiro-fuels are synthesized from lignocellulose-derived cyclic ketones for the first time, which show higher density, higher neat heat of combustion and lower freezing point compared with other biofuels synthesized from the same feedstock, and thus represent a new type of renewable high-density fuel attractive for practical applications.
Co-reporter:Zhen-Feng Huang; Jiajia Song; Ke Li; Muhammad Tahir; Yu-Tong Wang; Lun Pan; Li Wang; Xiangwen Zhang
Journal of the American Chemical Society 2016 Volume 138(Issue 4) pp:1359-1365
Publication Date(Web):January 16, 2016
DOI:10.1021/jacs.5b11986
The development of highly active, universal, and stable inexpensive electrocatalysts/cocatalysts for hydrogen evolution reaction (HER) by morphology and structure modulations remains a great challenge. Herein, a simple self-template strategy was developed to synthesize hollow Co-based bimetallic sulfide (MxCo3–xS4, M = Zn, Ni, and Cu) polyhedra with superior HER activity and stability. Homogenous bimetallic metal–organic frameworks are transformed to hollow bimetallic sulfides by solvothermal sulfidation and thermal annealing. Electrochemical measurements and density functional theory computations show that the combination of hollow structure and homoincorporation of a second metal significantly enhances the HER activity of Co3S4. Specifically, the homogeneous doping in Co3S4 lattice optimizes the Gibbs free energy for H* adsorption and improves the electrical conductivity. Impressively, hollow Zn0.30Co2.70S4 exhibits electrocatalytic HER activity better than most of the reported nobel-metal-free electrocatalysts over a wide pH range, with overpotentials of 80, 90, and 85 mV at 10 mA cm–2 and 129, 144, and 136 mV at 100 mA cm–2 in 0.5 M H2SO4, 0.1 M phosphate buffer, and 1 M KOH, respectively. It also exhibits photocatalytic HER activity comparable to that of Pt cocatalyst when working with organic photosensitizer (Eosin Y) or semiconductors (TiO2 and C3N4). Furthermore, this catalyst shows excellent stability in the electrochemical and photocatalytic reactions. The strategy developed here, i.e., homogeneous doping and self-templated hollow structure, provides a way to synthesize transition metal sulfides for catalysis and energy conversion.
Co-reporter:Muhammad Tahir, Nasir Mahmood, Lun Pan, Zhen-Feng Huang, Zhe Lv, Jingwen Zhang, Faheem. K. Butt, Guoqiang Shen, Xiangwen Zhang, Shi Xue Dou and Ji-Jun Zou
Journal of Materials Chemistry A 2016 vol. 4(Issue 33) pp:12940-12946
Publication Date(Web):23 Jul 2016
DOI:10.1039/C6TA05088C
The development of low cost and durable electrocatalysts for the oxygen evolution reaction (OER) for water splitting remains a great challenge. Here, we developed strongly coupled hybrid nanowires (NWs) of anion (Cl− and CO−) doped cobalt hydroxide coated with nanosheets of graphitic carbon nitride (Co(OH)2@g-C3N4) through an in situ hydrothermal method. With 5% g-C3N4 added in the synthesis, we obtained perfectly coated Co(OH)2 by g-C3N4 nanosheets with an overall diameter of ∼110 nm and a coating layer of ∼10 nm. The structural and compositional analyses confirm the strong interaction between g-C3N4 and Co(OH)2 that makes the hybrid highly effective for the OER. As a result Co(OH)2@g-C3N4 NWs exhibit an excellent over-potential of 0.32 V at 10 mA cm−2 as well as extraordinary stability, which are better than those of the state-of-the-art noble metals (IrO2 and RuO2) and most reported Co- and C3N4-based electrocatalysts although both Co(OH)2 and g-C3N4 separately display very fair performance. Furthermore, a combination of Co(OH)2@g-C3N4 and Pt/C delivers a current density of 80 mA cm−2 at 1.9 V for overall water splitting.
•Aldol condensation of cyclic ketones and furanic aldehydes takes place easily.•Solvent-free reaction gives higher activity than diluted reaction.•Yield above 85% was achieved under moderate conditions.•Biofuels have density of 0.81–0.82 g/ml.Transferring lignocellulose-derived compounds to cyclic hydrocarbons via aldol condensation has great potential in synthesizing high-density biofuel. But current synthesis involves large amount of solvent that inevitably affects the production efficiency. Herein, we synthesized high-density biofuel efficiently using solvent-free condensation of cyclopentanone/cyclohexanone and furfural/5-hydroxymethylfurfural. It is found that the solvent-free reaction gives much higher conversion than the diluted one does, for example 86.7% vs 62.7% for cyclopentanone/furfural condensation, and the selectivity of condensed product is above 90.0%. The reaction rate slows down when the reactant is changed from cyclohexanone to cyclopentanone or from furfural to 5-hydroxymethylfurfural, but can be improved by simply increases the dosage of catalyst or reaction temperature. As a result, the yield over 85.0% is obtained for the condensation reactions. Subsequently, the condensed products were converted to branched cyclic hydrocarbons with selectivity of about 70–80%. Their density increases from 0.815 g/ml to 0.826 g/ml with the increase of carbon number, with the freezing point increasing from − 24.6 °C to − 9.5 °C. They have very low viscosity and can be used as liquid fuels alone or blended with other fuels.
Co-reporter:Hongling Niu, Jinhui Lu, JiaJia Song, Lun Pan, Xiangwen Zhang, Li Wang, and Ji-Jun Zou
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 31) pp:8527
Publication Date(Web):May 1, 2016
DOI:10.1021/acs.iecr.6b00984
Heterogeneous catalytic hydrogenation of nitroarenes is one of the most important chemical transformations, and exploring earth-abundant catalysts is very attractive for application. Herein, we studied the catalytic activity of several iron oxide catalysts with similar structure and surface area. It is found that γ-Fe2O3, α-Fe2O3, and FeO show obvious but a little limited activity, but the activity of the used catalyst is increased in the second run, especially for γ-Fe2O3. Characterization shows that Fe2O3 is partly reduced with many oxygen vacancies produced on the surface, which accounts for the high hydrogenation activity. Finally, Fe3O4 exhibits activity significantly higher than Fe2O3 and FeO, and 100% selectivity in the hydrogenation of nitroarenes to anilines. Also, Fe3O4 is easy to separate by a magnetic field and shows excellent recycling stability.
Co-reporter:Xiu-tian-feng E, Lun Pan, Fang Wang, Li Wang, Xiangwen Zhang, and Ji-Jun Zou
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 10) pp:2738-2745
Publication Date(Web):February 25, 2016
DOI:10.1021/acs.iecr.6b00043
Nanofluid fuels containing energetic nanoparticles (NPs) are a very promising high-density fuel as the presence of NPs can significantly enhance the fuel’s density and energy. Here we reported a comprehensive study on nanofluid fuels through theoretical and experimental methods. Theoretical calculation shows aluminum (Al) is very effective in improving the volumetric specific impulsion and density. Then, a surface-modification method was developed, and oleic acid is the most effective to stabilize Al NPs in fuel. The surface modification inhibits the contact and agglomeration of NPs and makes them stably dispersed in fuel. With the addition of 30% Al NPs, the density and volumetric energy of JP-10 are increased by 20% and 10%, respectively, and the fuel can flow freely. Combustion test shows the combustion efficiency of Al NPs is higher than 95%, with density specific impulsion being increased by 15% through the addition of 16% Al NPs.
Co-reporter:Lun Pan, Songbo Wang, Jiawei Xie, Li Wang, Xiangwen Zhang, Ji-Jun Zou
Nano Energy 2016 Volume 28() pp:296-303
Publication Date(Web):October 2016
DOI:10.1016/j.nanoen.2016.08.054
•TiO2 p-n homojunction was fabricated by decorating n-type TiO2 QDs on p-type TiO2.•The p-n homojunction shows high efficiency in charge separation.•The p-n homojunction exhibits high photo-performances H2 generation.Constructing junctions between semiconductors is an effective way to promote charge separation and thus to improve the photoelectrochemical and photocatalytic H2 generation, and specifically, p-n homojunction is considered as a very promising structure. Herein, we fabricate TiO2 p-n homojunction by in-situ decorating n-type oxygen-defected TiO2 QDs on p-type titanium-defected TiO2 surface. The composite structure and O-/Ti-vacancies are testified by TEM, XRD, XPS, EPR and UV–vis DRS characterizations. The “V-shaped” Mott-Schottky plot and anodic shift of onset potential in I-V curves verify the characteristics of p-n homojunction. PL and EIS analyses indicate p-n homojunction is much more efficient in charge separation and transfer than p-type, n-type and n-n type-II homojunction, subsequently leading to the significantly high photoactivity. Compared with p-TiO2, p-n homojunction TiO2 possesses 5-fold and 1.7-fold higher performances in photoelectrochemical and photocatalytic hydrogen generation, respectively. This work provides new opportunities to design and fabricate highly efficient TiO2 photocathodes for hydrogen generation.
The conversion, storage, and utilization of renewable energy have all become more important than ever before as a response to ever-growing energy and environment concerns. The performance of energy-related technologies strongly relies on the structure and property of the material used. The earth-abundant family of tungsten oxides (WOx≤3) receives considerable attention in photocatalysis, electrochemistry, and phototherapy due to their highly tunable structures and unique physicochemical properties. Great breakthroughs have been made in enhancing the optical absorption, charge separation, redox capability, and electrical conductivity of WOx≤3 through control of the composition, crystal structure, morphology, and construction of composite structures with other materials, which significantly promotes the efficiency of processes and devices based on this material. Herein, the properties and synthesis of WOx≤3 family are reviewed, and then their energy-related applications are highlighted, including solar-light-driven water splitting, CO2 reduction, and pollutant removal, electrochromism, supercapacitors, lithium batteries, solar and fuel cells, non-volatile memory devices, gas sensors, and cancer therapy, from the aspect of function-oriented structure design and control.
Journal of the American Chemical Society 2015 Volume 137(Issue 8) pp:2975-2983
Publication Date(Web):February 6, 2015
DOI:10.1021/ja512047k
Defects are critically important for metal oxides in chemical and physical applications. Compared with the often studied oxygen vacancies, engineering metal vacancies in n-type undoped metal oxides is still a great challenge, and the effect of metal vacancies on the physiochemical properties is seldom reported. Here, using anatase TiO2, the most important and widely studied semiconductor, we demonstrate that metal vacancies (VTi) can be introduced in undoped oxides easily, and the presence of VTi results in many novel physiochemical properties. Anatase Ti0.905O2 was synthesized using solvothermal treatment of tetrabutyl titanate in an ethanol–glycerol mixture and then thermal calcination. Experimental measurements and DFT calculations on cell lattice parameters show the unstoichiometry is caused by the presence of VTi rather than oxygen interstitials. The presence of VTi changes the charge density and valence band edge of TiO2, and an unreported strong EPR signal at g = 1.998 presents under room temperature. Contrary to normal n-type and nonferromagnetic TiO2, Ti-defected TiO2 shows inherent p-type conductivity with high charge mobility, and room-temperature ferromagnetism stronger than Co-doped TiO2 nanocrystalline. Moreover, Ti-defected TiO2 shows much better photocatalytic performance than normal TiO2 in H2 generation (4.4-fold) and organics degradation (7.0-fold for phenol), owing to the more efficient charge separation and transfer in bulk and at semiconductor/electrolyte interface. Metal-defected undoped oxides represent a unique material; this work demonstrates the possibility to fabricate such material in easy and reliable way and thus provides new opportunities for multifunctional materials in chemical and physical devices.
Co-reporter:Jiajia Song, Zhen-Feng Huang, Lun Pan, Ji-Jun Zou, Xiangwen Zhang, and Li Wang
ACS Catalysis 2015 Volume 5(Issue 11) pp:6594
Publication Date(Web):October 5, 2015
DOI:10.1021/acscatal.5b01522
Heterogeneous hydrogenation is one of the most important industrial operations, and reduced metals (mostly noble metals and a few inexpensive metals) generally serve as the catalyst to activate molecular H2. Herein we report oxygen-deficient tungsten oxide, such as WO2.72, is a versatile and efficient catalyst for the hydrogenation of linear olefins, cyclic olefins, and aryl nitro groups, with obvious advantages compared with non-noble metal nickel catalyst from the aspect of activity and selectivity. Density functional theory calculations prove the oxygen-deficient surface activates H2 very easily in both kinetics and thermodynamics. Testing on several oxygen-deficient tungsten oxides shows a linear dependence between the hydrogenation activity and oxygen vacancy concentration. Tungsten is earth-abundant, and WO2.72 can be synthesized in large scale using a low-cost procedure, which provides an ideal catalyst for industrial application. Because oxygen vacancy is a common characteristic of many metal oxides, the findings in this work may be extended to other metal oxides and thus provide the possibility for exploring a new type of hydrogenation catalyst.Keywords: heterogeneous catalysis; hydrogenation; molecular H2 activatation; oxygen vacancy; tungsten oxide
Co-reporter:Qiang Deng, Genkuo Nie, Lun Pan, Ji-Jun Zou, Xiangwen Zhang and Li Wang
Green Chemistry 2015 vol. 17(Issue 8) pp:4473-4481
Publication Date(Web):08 Jul 2015
DOI:10.1039/C5GC01287B
Transferring biomass-derived cyclic ketones such as cyclopentanone and cyclohexanone to a mono-condensed product through aldol self-condensation has great potential for the synthesis of a renewable high-density fuel. However, the selectivity is low for numerous catalysts due to the rapid formation of di-condensed by products. Herein, MIL-101-encapsulating phosphotungstic acid is synthesized to catalyze the self-condensation with selectivity of more than 95%. PTA clusters are uniformly dispersed in MOF cages and decrease the empty space (pore size), which provides both acidic sites and shape-selective capability. The optimal PTA amount decreases corresponding to the increase of reactant size. The shape-selectivity is also realized by changing the pore size of MOF such as from MIL-101 to MIL-100. Moreover, the catalyst is resistant to PTA leaching and performs stably after 5 runs. After hydrodeoxygenation of the mono-condensed product, high-density biofuels with densities of 0.867 g ml−1 and 0.887 g ml−1 were obtained from cyclopentanone and cyclohexanone, respectively. This study not only provides a promising route for the production of high-density biofuel but also suggests the advantage of MOF-based catalysts for shape-selective catalysis involving large molecular size.
Co-reporter:Lun Pan, Guo-Qiang Shen, Jing-Wen Zhang, Xiao-Chu Wei, Li Wang, Ji-Jun Zou, and Xiangwen Zhang
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 29) pp:7226-7232
Publication Date(Web):July 3, 2015
DOI:10.1021/acs.iecr.5b01471
TiO2 and ZnO are extensively used photocatalysts, but their activity needs improvement due to rapid charge recombination. Herein, we designed and synthesized a novel structure of a TiO2–ZnO composite sphere decorated with ZnO clusters by a one-pot solvethermal method. TEM and EDX characterizations show this structure contains a TiO2 core, TiO2–ZnO composite (type II heterojunction) surface layer, and surface c-axis ZnO clusters. The in situ Au and PbO2 photodeposition shows that the photoinduced electrons and holes are driven to ZnO clusters and TiO2, respectively, attributed to the synergy of the type II heterojunction of TiO2–ZnO and high electron mobility of ZnO. The PL spectra confirm that such a structure is much more efficient in retarding the charge recombination than the sole TiO2–ZnO sphere. Importantly, this structure shows higher photoactivity in degradation of rhodamine B and isomerization of norbornadiene than pure TiO2, ZnO, and TiO2–ZnO composite spheres.
Co-reporter:Zhen-Feng Huang, Jiajia Song, Lun Pan, Ziming Wang, Xueqiang Zhang, Ji-Jun Zou, Wenbo Mi, Xiangwen Zhang, Li Wang
Nano Energy 2015 Volume 12() pp:646-656
Publication Date(Web):March 2015
DOI:10.1016/j.nanoen.2015.01.043
•Carbon nitride with simultaneous porous network and O-doping was “one-pot” fabricated.•It shows significantly enhanced optical absorption and charge transfer and separation.•It shows hydrogen evolution with AQE of 7.8% at 420 nm.•Synergetic interaction of porous network and O-doping is disccused.Efficient charge separation and broaden light absorption are of crucial importance for solar-driven hydrogen evolution reaction (HER), and graphitic carbon nitride (g-C3N4) is a very promising photocatalyst for this reaction. Here we report a facile precursor pre-treatment method, by forming hydrogen bond-induced supramolecular aggregates, to fabricate g-C3N4 with simultaneous novel porous network and controllable O-doping. Experimental and DFT computation identified that O doping preferentially occurs on two-coordinated N position, and the porous network and O-doping synergetically promote the light harvesting and charge separation. As a result, this material shows 6.1 and 3.1 times higher HER activity (with apparent quantum efficiency of 7.8% at 420 nm) than bulk and even 3D porous g-C3N4. This work highlights that simply pre-treating the precursor can not only control the architecture but also introduce helpful foreign atoms or monomer in the matrix, which provides a useful strategy to design and fabricate highly efficient g-C3N4 photocatalyst.This paper describes a facile precursor pre-treatment method, by forming hydrogen bond-induced supramolecular aggregates, to fabricate g-C3N4 with simultaneous novel porous network structure and O-doping. Experimental and DFT computation confirm simultaneous porous network structure and O-doping have synergetic promotion on light harvesting and charge separation. As a result, it shows remarkably higher HER activity (AQE=7.8% at 420 nm) than bulk and even 3D porous g-C3N4.
Co-reporter:Zhen-Feng Huang, Lun Pan, Ji-Jun Zou, Xiangwen Zhang and Li Wang
Nanoscale 2014 vol. 6(Issue 23) pp:14044-14063
Publication Date(Web):30 Sep 2014
DOI:10.1039/C4NR05245E
Water oxidation is the key step for both photocatalytic water splitting and CO2 reduction, but its efficiency is very low compared with the photocatalytic reduction of water. Bismuth vanadate (BiVO4) is the most promising photocatalyst for water oxidation and has become a hot topic for current research. However, the efficiency achieved with this material to date is far away from the theoretical solar-to-hydrogen conversion efficiency, mainly due to the poor photo-induced electron transportation and the slow kinetics of oxygen evolution. Fortunately, great breakthroughs have been made in the past five years in both improving the efficiency and understanding the related mechanism. This review is aimed at summarizing the recent experimental and computational breakthroughs in single crystals modified by element doping, facet engineering, and morphology control, as well as macro/mesoporous structure construction, and composites fabricated by homo/hetero-junction construction and co-catalyst loading. We aim to provide guidelines for the rational design and fabrication of highly efficient BiVO4-based materials for water oxidation.
Co-reporter:Zhen-Feng Huang, Jiajia Song, Lun Pan, Xu Jia, Zhe Li, Ji-Jun Zou, Xiangwen Zhang and Li Wang
Nanoscale 2014 vol. 6(Issue 15) pp:8865-8872
Publication Date(Web):08 May 2014
DOI:10.1039/C4NR00905C
Top-down nanostructure engineering and band engineering are promising methods for fabricating efficient photocatalysts with enhanced optical and electronic properties; however, composites with simultaneously engineered structure and band are very rare. Herein, we constructed a unique architecture composed of a W18O49 nanowire alignment core and porous BiOCl shell (WA@BiOCl), which combined the advantages of both an assembly structure and a type II core–shell heterojunction. The W18O49 alignments (WA) were synthesized using a “one-pot” solvothermal treatment of WCl6/NaNO3via NO3−-mediated assembly, whereas the W18O49 nanowires with BiOCl shell (W@BiOCl) were obtained using WCl6/BiCl3. Then, WA@BiOCl, in contrast to W@BiOCl alignments, were fabricated when WCl6 and Bi(NO3)3 were present in the starting mixture. Optical absorption, photoelectrochemical measurements and photoluminescence characterizations show that either the alignments or the core–shell heterojunctions can enhance light harvesting, photo-charge transfer and collection. As a synergetic result, the WA@BiOCl architecture exhibited very high photoactivity and photostability. Under UV-vis (or vis) irradiation, WA@BiOCl is 2.43 (1.93), 3.93 (2.73) and 5.34 (3.44)-fold more active than W@BiOCl, WA and W18O49, respectively. The results demonstrate that the simultaneous nanostructure and band engineering can produce a more efficient photocatalyst than a single strategy alone, which suggests a potential method for the fabrication of photocatalysts in the fields of environment and energy.
Co-reporter:Zhen-Feng Huang, Jiajia Song, Lun Pan, Fenglei Lv, Qingfa Wang, Ji-Jun Zou, Xiangwen Zhang and Li Wang
Chemical Communications 2014 vol. 50(Issue 75) pp:10959-10962
Publication Date(Web):26 Jun 2014
DOI:10.1039/C4CC02201G
Mesoporous hollow W18O49 spheres were fabricated by a facile solvent-induced assembly method using anhydrous WCl6 as a precursor and CH3COOH as a solvent. This unique structure exhibited remarkably enhanced photocatalytic and photoelectrocatalytic performance than other morphologies like urchin and nanowire due to the simultaneous enhancement in light harvesting, surface area and adsorption capability.
Co-reporter:Lun Pan, Songbo Wang, Ji-Jun Zou, Zhen-Feng Huang, Li Wang and Xiangwen Zhang
Chemical Communications 2014 vol. 50(Issue 8) pp:988-990
Publication Date(Web):18 Nov 2013
DOI:10.1039/C3CC47752E
V-doped TiO2 quantum dots (QDs) possessing many Ti3+ defects were fabricated by simple hydrolysis using MCM-41 as a support. The QDs show high charge-separation efficiency and high photocatalytic activity due to the quantum size effect and the newly formed defect- and dopant-mediated band levels.
Co-reporter:Lun Pan, Ren Feng, Hao Peng, Xiu-tian-feng E, Ji-Jun Zou, Li Wang and Xiangwen Zhang
RSC Advances 2014 vol. 4(Issue 92) pp:50998-51001
Publication Date(Web):06 Oct 2014
DOI:10.1039/C4RA08868A
Quadricyclane (QC), synthesized from photoisomerization and commonly used for solar-energy conversion and storage, is found to be an excellent hypergolic fuel. The ignition delay time of QC–N2O4 is 29 ms, which is decreased to 18 ms by addition of boron nanoparticles. Importantly, quadricyclane has 18.9% higher specific impulsion than currently used but dangerous dimethylhydrazine.
Co-reporter:Xiu-tian-feng E, Yu Zhang, Ji-Jun Zou, Xiangwen Zhang, Li Wang
Materials Letters 2014 Volume 118() pp:196-199
Publication Date(Web):1 March 2014
DOI:10.1016/j.matlet.2013.12.066
•Unexpected time-dependent shape evolution of Au NPs in the Brust–Schiffrin synthesis is observed.•The evolution is a kinetic-to-thermodynamic control process.•Various thermodynamically unfavored shapes are formed during the evolution.•Well-defined triangular plates can be produced considerably by tuning the types of protecting ligands.The shape evolution and control in the Brust–Schiffrin synthesis of Au nanoparticles (NPs) is presented in this work. Different from the current wisdom, Au NPs undergoes a time-dependent shape evolution. At the beginning, small spherical NPs are produced as reported before. With prolonged time, however, big NPs with many thermodynamically unfavored shapes such as triangle and truncated triangle are formed. And they are ultimately transferred into spherical shape bigger than the original NPs. It is suggested that the shape evolution is a kinetic-to-thermodynamic control process, during which, well-defined triangular plates are produced considerably by tuning the types of protecting ligands. This reveals the potential of fabricating not only size but also shape controllable metal NPs using the popular Brust–Schiffrin synthesis.Au nanoparticles in Brust–Schiffrin synthesis undergo a time-dependent shape evolution, suggesting the potential of fabricating both size and shape controllable metal nanoparticles.
Co-reporter:Lun Pan ; Ji-Jun Zou ; Tierui Zhang ; Songbo Wang ; Zhe Li ; Li Wang ;Xiangwen Zhang
The Journal of Physical Chemistry C 2014 Volume 118(Issue 30) pp:16335-16343
Publication Date(Web):October 23, 2013
DOI:10.1021/jp408056k
A hydrothermal approach is developed to fabricate Cu2O film via in situ redox reaction between Cu2+ and Cu plate. The crystallization process under different conditions was demonstrated, and the crystal structure of Cu2O was verified by XRD, Raman and XPS characterizations. Simply tuning the anionic groups of Cu2+ can generate different morphologies including rod-like arrays, cross-linked and truncated octahedrals. Mott–Schottky plots and PL spectra indicate that the rod-like arrays possess more copper vacancies than the other two morphologies. In photodegradation, the rod arrays exhibit much better performance, following by truncated and then cross-linked octahedrals. The photostability of the three morphologies was also determined. Although different surface reconstructions occur for the films owing to different charge transfer and consumption pathway, their photoactivities are all enhanced after the first run. Then rod arrays and cross-linked octahedrals show very stable activity, but truncated octahedrals show a gradually decreased activity. This work may be helpful for rationally modulating Cu2O-based materials and understanding their deactive mechanism in photocatalysis.
•Zn defected ZnO were fabricated by solvothermal treatment and thermal calcination.•Zn vacancies led to p-type conductivity and room-temperature ferromagnetism.•Zn vacancies also led to high photocatalytic activity.•The formation process of Zn vacancies during the synthesis was investigated.Abundant Zn vacancies (7.5 mol%) were successfully introduced into undoped ZnO by a simple solvothermal method followed with thermal calcination, and undoubtedly proved by both characterizations and computations. The presence of Zn vacancies led to some new properties in ZnO, such as p-type conductivity, room-temperature ferromagnetism and high photocatalytic activity. The formation process of abundant Zn vacancies during the synthesis of ZnO was also discussed. This work demonstrates that metal defects can be easily engineered in undoped metal oxides, which may trigger many unexpected behaviors and thus widen the synthetic approach and application of functional materials in energy fields.
Co-reporter:Lun Pan, Ji-Jun Zou, Songbo Wang, Zhen-Feng Huang, Ao Yu, Li Wang and Xiangwen Zhang
Chemical Communications 2013 vol. 49(Issue 59) pp:6593-6595
Publication Date(Web):24 Apr 2013
DOI:10.1039/C3CC42152J
Quantum dot (TiO2) self-decorated and defect-free anatase nanosheets were fabricated by a long-time hydrothermal strategy and subsequent defect healing. Such decoration provides a new and effective charge transfer pathway over the nanosheet surface, leading to remarkably high photoactivity.
Co-reporter:Tingting Ma, Ren Feng, Ji-Jun Zou, Xiangwen Zhang, and Li Wang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 7) pp:2486-2492
Publication Date(Web):January 25, 2013
DOI:10.1021/ie303227g
Rearrangement of three types of fused polycyclic hydrocarbons with carbon atoms 12–14 was conducted using chloroaluminate ionic liquid (IL) as acid catalyst. The hydrocarbons undergo quick configurational isomerization and then skeletal rearrangement toward alkyl-adamantanes. Although having different molecular structure, these hydrocarbons all lead to adamantanes substituted with 2–3 methyl and/or ethyl groups. The alkyl-adamantanes show high density, low freezing point and viscosity, and are very attractive as high-density fuels. Computation using density functional theory confirms that alkyl-adamantanes are thermodynamically favored and explains the experimental product distribution very well. On this basis, the reaction pathway of each hydrocarbon was illustrated. The reaction conditions including acidity (AlCl3 fraction), temperature, and IL dosage show significant effect on the rearrangement. Moreover, the distribution of alkyl-adamantanes can be tuned by adjusting the reaction conditions, allowing the fuels’ properties to be fine-tuned. This work provides a versatile route to synthesizing alkyl-diamondoid fuels using simple chemical feedstocks in an effective way.
Dye sensitization and nonmetal doping on TiO2 are important for visible-light utilization in many fields. In this work, N, N&S and N&F doped hierarchical macro-/mesoporous TiO2 was prepared using hydrothermal method. Most of the nonmetals exist as surface impurities before calcination, without any visible-light response. Thermal calcination makes N effectively implanted into TiO2 lattice and causes red shift in optical absorption, but S and F are mainly on the surface. The activity of prepared samples for the photodegradation of rhodamine B under visible light was evaluated. The reaction over doped samples without calcination proceeds solely via self-sensitization, and calcination effectively enhances the photodegradation due to nonmetal doping. After being stored for ca. half a year, the activity of all samples are promoted significantly due to the water-mediated adsorption switch from covalent to electrostatic adsorption, caused by pre-bonding of water to surface bridging hydroxyls. The activity of doped samples is further enhanced with water treatment, attributed to the formation of more water-mediated electrostatic modes. The combination of nonmetal doping and water-mediated adsorption switch greatly enhances the visible-light activity of TiO2 (e.g., water-treated N&F-codoped sample shows 6.8-fold higher activity than pure TiO2).
Modulation of anatase toward highly active facets has been attracting much attention, but the mechanism and photoactivity are still ambiguous. Here we demonstrate the inherent mechanisms for facets nucleation and morphology evolution, and clarify some vital influences of facets and surface nature on the photoactivity. Simply tuning the Ti/F ratio in the synthetic mixture leads to single anatase crystal exposed with different facets like {001}, {010}, or {110}. And complex sphere structure exposed with {001} facets can be formed by secondary nucleation and growth. Prolonging the hydrothermal treatment time causes selective etching on {001} facets, whereas defluorination via thermal calcination produces many pores on the surface. The photodegradation of positively and negatively charged, and zwitterionic dyes indicates that the type of reactant, adsorption mode and surface area play significant roles in photocatalysis. This work makes a step toward understanding the formation of facet-mediated structure and designing highly active materials for environmental remediation, hydrogen production, and dye-sensitized solar cells.Keywords: crystal growth; facets; morphology; photocatalysis; titanium dioxide;
Co-reporter:Lun Pan, Ji-Jun Zou, Xin-Yu Liu, Xiao-Jing Liu, Songbo Wang, Xiangwen Zhang, and Li Wang
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 39) pp:12782
Publication Date(Web):September 6, 2012
DOI:10.1021/ie3019033
Hierarchical TiO2 was prepared via hydrolysis method and characterized by XRD, N2 adsorption–desorption, UV–vis diffusion, and NH3–TPD. With the increase of calcination temperature, the surface area and surface hydroxyls of prepared materials decrease rapidly. The photoactivity was evaluated using the self-sensitized photodegradation of rhodamine B under visible light. The fresh samples show higher activity than P-25 due to higher surface area and more effective light utilization. After stored in air for ca. half a year, the materials show significantly increased photoactivity, due to the prebonding of water on surface bridging hydroxyls, which induces water-mediated adsorption switch from covalent mode to electrostatic one. Water treatment further promotes the photoactivity of stored samples, because more water are bonded on TiO2 surface. It is found that the water-mediated effect closely depends on the surface area and amount of surface bridging hydroxyls.
Co-reporter:Ren Feng, Ji-Jun Zou, Xiangwen Zhang, Li Wang, and Haitao Zhao
The Journal of Organic Chemistry 2012 Volume 77(Issue 22) pp:10065-10072
Publication Date(Web):October 22, 2012
DOI:10.1021/jo3015616
A computational study using a hybrid DFT method (M06) on the cyclopropanation of endo-dicyclopentadiene with Simmons–Smith zinc carbenoids is reported. Each channel proceeds via the methylene-transfer mechanism with a reactant complex (RC) and subsquently a asynchronous transition state (TS). The channels with monomeric IZnCH2I attacking the double bonds from the exo-face have a much lower barrier (about 16.17–18.43 kcal/mol) in the gas phase, compared with the channels from the endo-face (21.80–31.13 kcal/mol). Thus, P1 and P3 are the primary cyclopropanated compounds, and P5 is the sole final product, representing remarkable stereospecificity. When considering the bulk solvent effect of diethyl ether, the barriers are decreased about 0.50–7.77 kcal/mol due to more “destabilization”of RC than TS. The solvated (ICH2)2Zn can further reduce the barriers about 0.18–2.30 kcal/mol. In addition, the solvated IZnCH2I and (ICH2)2Zn do not change the reaction pathways and retain the stereospecificity. Our computational results agree with the experimental observations quite well and suggest that both IZnCH2I and (ICH2)2Zn might be the active species in the real reaction system. Regarding the solvent effect, the polar continuum model is more realistic than the direct involvement of diethyl ether molecules.
Co-reporter: Ji-Jun Zou;Na Chang; Xiangwen Zhang ; Li Wang
ChemCatChem 2012 Volume 4( Issue 9) pp:1289-1297
Publication Date(Web):
DOI:10.1002/cctc.201200106
Abstract
A series of Al-incorporated mobile crystalline materials (Al-MCM-41) were prepared by hydrothermal synthesis and characterized by XRD, N2 adsorption (isotherms), inductively coupled plasma (ICP) analysis, 27Al magic angle spinning (MAS) NMR spectroscopy, and in situ pyridine adsorption (IR analysis). All samples exhibit an ordered structure with the majority of Al species in framework positions, except those with an SiO2/Al2O3 ratio ≤10. The concentration of acid sites is closely related to the Al content in the unit cell. In the presence of Al-MCM-41, both α- and β-pinenes are quickly transformed into isomerized products, which then couple to form homo- and heterodimers. Lewis acid sites are active in triggering both the isomerization and dimerization reactions, but weak Brønsted acid sites seem inactive for the dimerization. Al-MCM-41 has a greater activity than many other microporous and layered materials, and can be easily regenerated. The activity correlates well with the concentration of acid sites, and the sample with an SiO2/Al2O3 ratio of 20 shows the highest activity.
Co-reporter:Lun Pan ; Ji-Jun Zou ; Xiangwen Zhang ;Li Wang
Journal of the American Chemical Society 2011 Volume 133(Issue 26) pp:10000-10002
Publication Date(Web):June 6, 2011
DOI:10.1021/ja2035927
Preadsorbed water along with surrounding bulk water significantly modulates the surface electronic structure of TiO2, switches the adsorption mode of dyes, and promotes dye sensitization of TiO2 under visible-light irradiation. This opens a door toward facile improvement in the efficiency of photodegradation of dyes and dye-sensitized solar cells under visible-light irradiation without any complicated and expensive surface modulation.
Co-reporter:Lei Wang, Ji-Jun Zou, Xiangwen Zhang, and Li Wang
Energy & Fuels 2011 Volume 25(Issue 4) pp:1342-1347
Publication Date(Web):March 22, 2011
DOI:10.1021/ef101702r
As a work successive to AlCl3 catalytic isomerization of tetrahydrotricyclopentadiene (THTCPD) [Wang, L.; Zhang, X.; Zou, J.-J.; Han, H.; Li, Y; Wang, L. Energy Fuels 2009, 23 (5), 2383−2388], the reaction using chloroaluminate ionic liquid (IL) was investigated. It is found that IL catalysis gives totally different product distribution. The endo-cycloproyl fragments of THTCPD that cannot be isomerized by AlCl3 catalysis are transferred to exo conformation easily. Furthermore, the hydrocarbons are transferred to diamondoids, including methyl-1,2-tetramethyleneadamantane, methyl-diethyl-adamantane, and methyl-diamantane via skeletal rearrangement, with the first diamondoid as the primary and dominant product (selectivity > 80%). The IL shows much higher activity than superacid CF3SO3H, attributed to the synergetic effect of strong acidity and the novel solvent environment. Increasing the temperature, IL dosage, and AlCl3 in IL can promote the rearrangement rate with a slight decrease in the selectivity of methyl-1,2-tetramethyleneadamantane. The presence of trace water in IL forms superacid and induces considerable cracking byproducts, and solvent typically used in rearrangement decreases the reaction rate. The diamondoid-based product shows a low freezing point and high hydrogen content and, thus, is superior as a high-energy-density fuel. This work may open a door for facile synthesis of diamondoid fuel.
Co-reporter:Lun Pan, Ji-Jun Zou, Xiangwen Zhang and Li Wang
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 18) pp:8526-8531
Publication Date(Web):August 5, 2010
DOI:10.1021/ie100841w
Metal(V, Fe, Ce, Cu, Cr)-doped TiO2 were synthesized for the photoisomerization of norbornadiene. Characterizations indicate that V and Fe are located in the substitutional sites of TiO2, Ce ions dispersed in the interstitial sites, while Cr and Cu aggregated on the surface. The order of activity is Fe−TiO2 > V−TiO2 > Cr−TiO2 > Ce−TiO2 > TiO2 > Cu−TiO2, suggesting the local structure and type of dopant are crucial. Materials with various V and Fe content were further studied. Fe ions are well dispersed in TiO2 lattice even at high metal content, whereas many separated V2O5 phases are formed. The activity of V−TiO2 changes with V content and the optimal Ti/V ratio is 15, but the activity of Fe−TiO2 is independent of the metal content. Attributed to the high dispersion, Fe−TiO2 is much more active than V−TiO2. The photoreactivity is correlated with the surface lattice oxygen, and a mechanism is proposed to explain the photoisomerization and role of Fe dopant.
Co-reporter:Yunhua Li, Ji-Jun Zou, Xiangwen Zhang, Li Wang, Zhentao Mi
Fuel 2010 Volume 89(Issue 9) pp:2522-2527
Publication Date(Web):September 2010
DOI:10.1016/j.fuel.2009.11.020
Tricyclopentadiene (TCPD), product of dicyclopentadiene (DCPD)/cyclopentadiene (CPD) cycloaddition, is a promising candidate as high-energy–density fuel. Thermal [4 + 2] cycloaddition of DCPD and CPD was simulated using M05-2X/6-311G(d,p) to predict the product distribution. There are four concerted but slightly asynchronous pathways leading to four adducts for endo-DCPD/CPD and exo-DCPD/CPD additions, respectively. The pathways connecting endo-adduct are kinetically preferred compared with those connecting exo-adduct. NB-adducts show higher stability than corresponding CP-adducts. Moreover, exo-isomers are more stable for CP-adducts, but the tendency is inverse for NB-adducts. The predicted product preference is NB-endo > CP-endo > CP-exo > NB-exo. Experiment shows product composition of NB-endo:CP-endo = 7.32:1 and NB-endo:CP-endo:CP-exo = 3.79:1:0.1 for thermal endo-DCPD/CPD and exo-DCPD/CPD additions, respectively, consistent with the predicted result. However, catalytic reaction gives completely different distribution, in which [4 + 2] NB-exo and CP-exo, along with at least 21.6% [2 + 2] adducts, are formed.
Ion pair “leakage” pathways, located computationally by means of multidimensional potential energy surface scans, rationalize the unsymmetrical D-label scrambling observed experimentally in the DCl addition products of nortricyclene and norbornene. “Classical” addition transition structures can interconvert (“leak”) to symmetrical nonclassical 2-norbornyl ion pair species, either TS’s or a minimum, before products form.
Co-reporter:Lei Wang, Xiangwen Zhang, Ji-Jun Zou, Hong Han, Yunhua Li and Li Wang
Energy & Fuels 2009 Volume 23(Issue 5) pp:2383
Publication Date(Web):April 17, 2009
DOI:10.1021/ef801139h
Here we used AlCl3 to transform tetrahydrotricyclopentadiene (THTCPD) into a high-energy-density liquid fuel. The reactant contains three inseparable isomers (I, II, and III). Quantum computation shows the possibility of endo fragments of THTCPD turning into exo counterparts. However, experiment indicates the isomerization only happens on norbornyl fragments but cyclopropyl fragments remain unchanged. Reactants I and II containing both norbornyl and cyclopropyl fragments are slowly isomerized, and the reactions are reversible, whereas III without a cyclopropyl fragment is converted quickly. The effects of the reaction conditions were studied. A 5% concentration of AlCl3 shows enough catalytic activity. A temperature higher than 15 °C is not preferred because it lowers the equilibrium conversion. A halohydrocarbon solvent such as 1,2-dichloroethane is necessary. Pseudo-first-order reversible kinetics was established for the isomerization of I and II. The heat of reaction is 22.94 and 17.69 kJ/mol, respectively. The resulting mixture shows good potential for advanced propulsion due to its high energy content and low freezing point.
Co-reporter:Ji-Jun Zou, Yan Xu, Xiangwen Zhang, Li Wang
Applied Catalysis A: General (16 April 2012) Volumes 421–422() pp:
Publication Date(Web):16 April 2012
DOI:10.1016/j.apcata.2012.01.035
The isomerization of endo-dicyclopentadiene (endo-DCPD) using Al-grafted MCM-41 was studied as an industrial practical synthesis route for exo-DCPD. The catalyst was prepared with post-synthesis grafting method, characterized by XRD, N2 adsorption/desorption, 27Al and 29Si MAS NMR, in-situ pyridine adsorption IR and NH3-TPD. The materials retain ordered mesoporous structure and high surface area. Al atoms are preferentially anchored in tetra-coordination, but these in octa-coordination increase significantly in case of high Al content. The amount of Brønsted acid is closely related to the amount of tetra-coordinated Al species whereas that of Lewis acid corresponding to the total Al content. The prepared material shows higher activity than microporous zeolites because its mesoporous structure gives free diffusion and excellent coke tolerance capability. A good correlation between the conversion of endo-DCPD and the amount of Lewis acid was observed. Specifically, the weak Lewis acid sites catalyze the endo- to exo-isomerization, meanwhile the moderate ones account for the [2 + 2] cycloaddition of two DCDP molecules. Catalyst with Si/Al of 8 is most active due to its highest concentration of weak Lewis acid. Addition of inert solvent, relatively low reaction temperature and high catalyst dosage can improve the isomerization. The deactivated catalyst can be easily regenerated by calcination.Graphical abstractDownload high-res image (148KB)Download full-size imageHighlights► Al-grafted MCM-41 shows higher activity than Hβ. ► Weak Lewis acid sites are the active site. ► Sample with Si/Al ratio of 8 shows highest selectivity of 85%, with conversion of 70%. ► The deactivated catalyst is easily regenerated by calcination.
Co-reporter:Yong-Chao Zhang, Lun Pan, Jinhui Lu, Jiajia Song, Zheng Li, Xiangwen Zhang, Li Wang, Ji-Jun Zou
Applied Surface Science (15 April 2017) Volume 401() pp:
Publication Date(Web):15 April 2017
DOI:10.1016/j.apsusc.2017.01.031
•The mechanism of ethylene hydrogenation on perfect and oxygen defective Co3O4(110) is investigated by using DFT + U.•Oxygen vacancy promotes ethylene hydrogenation thermodynamically and kinetically.•The Co3O4 (110) facet is more active than the (111) one for ethylene hydrogenation.Crystal facet engineering and defect engineering are both critical strategies to improve the catalytic hydrogenation performance of catalyst. Herein, ethylene hydrogenation on the perfect and oxygen defective Co3O4(110) surfaces has been studied by using periodic density functional theory calculations. The results are compared with that on Co3O4(111) surface to clarify the problem of which facet for Co3O4 is more reactive, and to illuminate the role of oxygen vacancy. The low oxygen vacancy formation energy suggests that Co3O4(110) surface with defective site is easily formed. The whole mechanism of H2 dissociation and stepwise hydrogenation of ethylene to ethane is examined, and the most favorable pathway is heterolytic dissociation of H2 follows two stepwise hydrogenation of ethylene process. The results show that ethyl hydrogenation to ethane on perfect Co3O4(110) surface is the rate limiting step with an activation energy of 1.19 eV, and the presence of oxygen vacancy strongly reduces the activation energies of main elementary steps, and the activation energy of rate limiting step is only 0.47 eV. Compared with that on Co3O4(111), ethylene hydrogenation is preferred on Co3O4(110) surface. Therefore, Co3O4 with exposed (110) facet is predicted as an excellent catalyst for ethylene hydrogenation.Figure optionsDownload full-size imageDownload high-quality image (182 K)Download as PowerPoint slide
Co-reporter:Zhen-Feng Huang, Jiajia Song, Lun Pan, Fenglei Lv, Qingfa Wang, Ji-Jun Zou, Xiangwen Zhang and Li Wang
Chemical Communications 2014 - vol. 50(Issue 75) pp:NaN10962-10962
Publication Date(Web):2014/06/26
DOI:10.1039/C4CC02201G
Mesoporous hollow W18O49 spheres were fabricated by a facile solvent-induced assembly method using anhydrous WCl6 as a precursor and CH3COOH as a solvent. This unique structure exhibited remarkably enhanced photocatalytic and photoelectrocatalytic performance than other morphologies like urchin and nanowire due to the simultaneous enhancement in light harvesting, surface area and adsorption capability.
Co-reporter:Lun Pan, Ji-Jun Zou, Songbo Wang, Zhen-Feng Huang, Ao Yu, Li Wang and Xiangwen Zhang
Chemical Communications 2013 - vol. 49(Issue 59) pp:NaN6595-6595
Publication Date(Web):2013/04/24
DOI:10.1039/C3CC42152J
Quantum dot (TiO2) self-decorated and defect-free anatase nanosheets were fabricated by a long-time hydrothermal strategy and subsequent defect healing. Such decoration provides a new and effective charge transfer pathway over the nanosheet surface, leading to remarkably high photoactivity.
Co-reporter:Muhammad Tahir, Nasir Mahmood, Lun Pan, Zhen-Feng Huang, Zhe Lv, Jingwen Zhang, Faheem. K. Butt, Guoqiang Shen, Xiangwen Zhang, Shi Xue Dou and Ji-Jun Zou
Journal of Materials Chemistry A 2016 - vol. 4(Issue 33) pp:NaN12946-12946
Publication Date(Web):2016/07/23
DOI:10.1039/C6TA05088C
The development of low cost and durable electrocatalysts for the oxygen evolution reaction (OER) for water splitting remains a great challenge. Here, we developed strongly coupled hybrid nanowires (NWs) of anion (Cl− and CO−) doped cobalt hydroxide coated with nanosheets of graphitic carbon nitride (Co(OH)2@g-C3N4) through an in situ hydrothermal method. With 5% g-C3N4 added in the synthesis, we obtained perfectly coated Co(OH)2 by g-C3N4 nanosheets with an overall diameter of ∼110 nm and a coating layer of ∼10 nm. The structural and compositional analyses confirm the strong interaction between g-C3N4 and Co(OH)2 that makes the hybrid highly effective for the OER. As a result Co(OH)2@g-C3N4 NWs exhibit an excellent over-potential of 0.32 V at 10 mA cm−2 as well as extraordinary stability, which are better than those of the state-of-the-art noble metals (IrO2 and RuO2) and most reported Co- and C3N4-based electrocatalysts although both Co(OH)2 and g-C3N4 separately display very fair performance. Furthermore, a combination of Co(OH)2@g-C3N4 and Pt/C delivers a current density of 80 mA cm−2 at 1.9 V for overall water splitting.
Co-reporter:Lun Pan, Songbo Wang, Ji-Jun Zou, Zhen-Feng Huang, Li Wang and Xiangwen Zhang
Chemical Communications 2014 - vol. 50(Issue 8) pp:NaN990-990
Publication Date(Web):2013/11/18
DOI:10.1039/C3CC47752E
V-doped TiO2 quantum dots (QDs) possessing many Ti3+ defects were fabricated by simple hydrolysis using MCM-41 as a support. The QDs show high charge-separation efficiency and high photocatalytic activity due to the quantum size effect and the newly formed defect- and dopant-mediated band levels.
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