Co-reporter:Yi Shen, Yongfang Zhou, Zhihui Zhang, Kaijun Xiao
Journal of Industrial and Engineering Chemistry 2017 Volume 52(Volume 52) pp:
Publication Date(Web):25 August 2017
DOI:10.1016/j.jiec.2017.03.038
•Cobalt–copper oxalate was studied as catalysts for Fenton-degradation of Congo red.•The effects of experimental parameters were studied.•The products of degradation were identified and the pathway was proposed.•The mechanism of the cobalt–copper oxalate/H2O2 system was elaborated.Cobalt–copper oxalate and cobalt oxalate nanofibers were synthesized by a simple precipitation method and further examined as catalysts for the heterogeneous Fenton reaction. It was found that experimental parameters including initial pH of pollutant solution, concentrations of CR and H2O2, and reaction temperature affected the degradation of CR. Under optimized conditions of catalyst loading = 100 mg L−1, pollutant concentration = 100 mg L−1, H2O2 concentration = 3 wt%, temperature = 30 °C and pH = 9, the Cobalt–copper oxalate nanofibers could completely degrade the Congo red within 100 min. The degradation products were analyzed and the degradation pathway was revealed. Mechanistic studies revealed that hydroxyl radicals derived from the activation of H2O2 by metal centers were mainly responsible for the degradation of CR, and that copper played a critical role in the superior catalytic performance of cobalt–copper oxalate.Download high-res image (158KB)Download full-size image
Co-reporter:Bin Gong;Yaotian Peng;Ziyan Pan;Weiming Chen;Kaijun Xiao;Ling Zhang
Chemical Communications 2017 vol. 53(Issue 95) pp:12766-12769
Publication Date(Web):2017/11/28
DOI:10.1039/C7CC07397F
Herein, gram-scale monodisperse sulfonated polystyrene (SPS) nanospheres are synthesized and examined as a sorbent for the removal of heavy metal ions (Pb2+, Zn2+ and Cu2+). The resulting uniform SPS nanospheres exhibit remarkable adsorption capabilities and kinetics, facile regeneration and outstanding recyclability, affording promising applications in food engineering and water cleanup.
Co-reporter:Yi ShenBin Gong, Kaijun Xiao, Lei Wang
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 4) pp:
Publication Date(Web):January 6, 2017
DOI:10.1021/acsami.6b09573
One-dimensional (1D) anisotropic platinum-based nanowires are promising electrocatalysts in polymer electrolyte membrane fuel cells owing to the inherent structural merits. Herein, we report an in situ growth of ultrathin PtRh nanowires (diameters of 2–3 nm) on graphene nanosheets via the oriented attachment pathway. Mechanistic studies reveal that graphene nanosheets play a critical role in the nucleation and growth of PtRh nanowires. The resulting hybrid of PtRh nanowire decorated graphene nanosheets shows outstanding activity and durability toward ethanol electro-oxidation. It exhibits a specific current density of 2.8 mA cm–2 and a mass-normalized current density of 1 A mg–1 metal, which are 5.4 and 3.1 times those of the state-of-the-art Pt/C catalyst, respectively. After 2000 cyclic tests, it maintains 86% of the initial electrochemically active surface area, which is larger than that of 63% obtained from the Pt/C catalyst. The superior performance is attributed to the combination of the advantageous 1D morphological motif with the synergistic effects of PtRh alloys and graphene nanosheet support.Keywords: ethanol electro-oxidation; graphene nanosheets; graphene-mediated synthesis; polymer electrolyte membrane fuel cells; PtRh nanowires;
Co-reporter:Yi Shen, Ling Li, Jingyu Xi and Xinping Qiu
Journal of Materials Chemistry A 2016 vol. 4(Issue 16) pp:5817-5822
Publication Date(Web):17 Mar 2016
DOI:10.1039/C6TA01236A
We report a novel three-dimensional architecture, consisting of tungsten carbide nanocrystals which are intimately riveted to graphite felt fabrics by carbon nanosheets (CNS@WC/GF). The as-prepared CNS@WC/GF monolith is utilized as a binder-free hydrogen evolution reaction electrode in both acidic and alkaline solutions. It demonstrates remarkable activity as well as durability.
Co-reporter:Yi Shen, Aik Chong Lua, Jingyu Xi, and Xinping Qiu
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 5) pp:3464
Publication Date(Web):January 19, 2016
DOI:10.1021/acsami.5b11966
Developing cost-effective and efficient hydrogen evolution reaction (HER) electrocatalysts for hydrogen production is of paramount importance to attain a sustainable energy future. Reported herein is a novel three-dimensional hierarchical architectured electrocatalyst, consisting of platinum–copper–nickel nanoparticles-decorated carbon nanofiber arrays, which are conformally assembled on carbon felt fabrics (PtCuNi/CNF@CF) by an ambient-pressure chemical vapor deposition coupled with a spontaneous galvanic replacement reaction. The free-standing PtCuNi/CNF@CF monolith exhibits high porosities, a well-defined geometry shape, outstanding electron conductivity, and a unique characteristic of localizing platinum–copper–nickel nanoparticles in the tips of carbon nanofibers. Such features render PtCuNi/CNF@CF as an ideal binder-free HER electrode for hydrogen production. Electrochemical measurements demonstrate that the PtCuNi/CNF@CF possesses superior intrinsic activity as well as mass-specific activity in comparison with the state-of-the-art Pt/C catalysts, both in acidic and alkaline solutions. With well-tuned composition of active nanoparticles, Pt42Cu57Ni1/CNF@CF showed excellent durability. The synthesis strategy reported in this work is likely to pave a new route for fabricating free-standing hierarchical electrodes for electrochemical devices.Keywords: carbon nanofiber arrays; chemical vapor deposition; free-standing electrocatalysts; hydrogen evolution reaction; ternary platinum−copper−nickel nanoparticles
Co-reporter:Yi Shen, Ling Li, Kaijun Xiao, and Jingyu Xi
ACS Sustainable Chemistry & Engineering 2016 Volume 4(Issue 4) pp:2351
Publication Date(Web):February 23, 2016
DOI:10.1021/acssuschemeng.6b00030
Developing high-performance nanostructured sorbents for water treatment is of great importance. Herein, we report a facile strategy to fabricate three-dimensional hierarchical architectures by integrating carbon nanofibers (CNFs) into macroscopic graphite felt (GF) supports. The physicochemical properties of CNF@GF monoliths including surface areas, densities, porosities, and pore structures could be conveniently tuned by varying reaction time. The CNF@GF monoliths were utilized as advanced sorbents for the removal of Pb2+, Congo red, organic solvents, and oils from aqueous solutions. The characteristics of adsorption processes including kinetics, isotherms, and regeneration were investigated. It is demonstrated that the CNF@GF exhibits outstanding performance for water treatment in terms of adsorption capacities, recovering, and recyclability. As such, the versatile CNS@GF monoliths show great application potential for water treatment.Keywords: Congo red; Hierarchical carbon nanofiber arrays; Lead ions; Oil cleanup; Sorption isotherms and kinetics; Water purification;
Co-reporter:Yi Shen, Aik Chong Lua
Journal of Colloid and Interface Science 2016 Volume 462() pp:48-55
Publication Date(Web):15 January 2016
DOI:10.1016/j.jcis.2015.09.050
•Interconnected trimodal porous carbon synthesized by nanocasting method.•High surface area and large pore volume carbon as catalyst.•As-synthesized carbon provide abundant active sites and space for chemical reactions.•Carbon catalyst used for hydrogen production by thermal decomposition of methane.•Carbon catalyst produced high methane conversion and hydrogen yield.A new type of porous carbon with an interconnected trimodal pore system is synthesized by a nanocasting method using nanoparticulated bimodal micro-mesoporous silica particles as the template. The synthesized template and carbon material are characterized using transmission electron microscopy (TEM), field emission electron scanning microscopy (FESEM) and nitrogen adsorption–desorption test. The synthesized carbon material has an extremely high surface area, a large pore volume and an interconnected pore structure, which could provide abundant active sites and space for chemical reactions and minimize the diffusion resistance of the reactants. The resulting carbon is used as the catalyst for hydrogen production by the thermal decomposition of methane. The catalytic results show that the as-synthesized carbon in this study produces much higher methane conversion and hydrogen yield than the commercial carbon materials.TEM (A and B) and FESEM (C) micrographs of the as-synthesized carbon.
Co-reporter:Qi He, Yi Shen, Kaijun Xiao, Jingyu Xi, Xinping Qiu
International Journal of Hydrogen Energy 2016 Volume 41(Issue 45) pp:20709-20719
Publication Date(Web):7 December 2016
DOI:10.1016/j.ijhydene.2016.07.205
•Pt/GNS and Pt-CeO2−x/GNS were studied for alcohol oxidation in alkaline media.•The hybrid of GNS and ceria was a promising catalyst support in alkaline media.•The Pt-CeO2−x/GNS showed better catalytic performance than the Pt/GNS.•The two catalysts had superior activity in alkaline media than in acidic media.Platinum/graphene nanosheet and platinum–ceria/graphene nanosheet are prepared by a one-pot synthesis protocol and examined as electrocatalysts for the oxidation of methanol, ethanol, ethylene glycol, and glycerol in alkaline solutions. The activity of the catalysts is evaluated by cyclic voltammetry, linear sweeping voltammetry, and chronoamperometric tests. It is indicated that the addition of ceria is favorable for the oxidation of the alcohols. The platinum–ceria/graphene nanosheet catalyst exhibits higher current densities and superior durability in comparison with the platinum/graphene nanosheet. Maximum current densities of 1.1, 1.3, 3.2 and 2.5 A mg−1 Pt are obtained from the platinum–ceria/graphene nanosheet catalyst for the oxidation of methanol, ethanol, ethylene glycol, and glycerol, respectively. Notably, the current density values for the oxidation of ethylene glycol (3.2 A mg−1 Pt) and glycerol (2.5 A mg−1 Pt) are among the most active electrocatalysts reported in the literature. The activity of the catalysts in 1 M KOH solution is compared with that in 1 M H2SO4 solution. Both the platinum/graphene nanosheet and platinum–ceria/graphene nanosheet show superior performance in alkaline media.
Co-reporter:Yi Shen
The Journal of Physical Chemistry C 2016 Volume 120(Issue 12) pp:6659-6668
Publication Date(Web):March 3, 2016
DOI:10.1021/acs.jpcc.6b00426
Large-scale assembling of graphitic carbon nanosheets to a three-dimensional hierarchical structure is a great challenge. Herein we report a facile synthesis of hierarchical magnetic carbon nanosheet assemblies (MCNSAs) via an ambient-pressure chemical vapor deposition method. To explore the formation mechanism, the as-prepared MCNSAs as well as the intermediates of synthesis were extensively characterized. It was revealed that two different carbon deposition processes, i.e., the dissolution–precipitation process and graphitic defects triggered catalytic decomposition of methane, were involved in the formation of MCNSAs. The disclosed method is simple and environmentally friendly, which is favorable for large-scale production. The resulting MCNSAs possess large surface areas, bimodal pore structures, abundant defective sites, excellent chemical stability, and sufficient magnetism. Such features afford significant advantages for application in water cleaning. As a proof of concept, the sorption performance of MCNSAs is demonstrated by using Congo red and Pb2+ as model pollutants. The characteristics of the sorption process including kinetics, isotherms, recovery, regeneration, and recycling are investigated. The results indicate that the MCNSAs are a promising sorbent for water cleaning.
Co-reporter:Yi Shen, Zhihui Zhang and Kaijun Xiao
RSC Advances 2015 vol. 5(Issue 111) pp:91846-91854
Publication Date(Web):15 Oct 2015
DOI:10.1039/C5RA18923C
A series of CoO, Co0.75Cu0.25O, Co0.5Cu0.5O and CuO nanoparticles were synthesized via the calcination of corresponding oxalates and further examined as catalysts for the heterogeneous Fenton reaction. The structures of the as-prepared oxides were characterized by field emission electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The catalytic activity of the oxides was evaluated by the degradation of Congo red. It was found that, among the four catalysts, Co0.5Cu0.5O showed the best catalytic performance. Subsequently, the effects of operating parameters including the substrate concentration, pH, H2O2 concentration and reaction temperature in the catalytic performance of the Co0.5Cu0.5O were systematically studied. Under optimized conditions of catalyst loading = 200 mg L−1, pollutant concentration = 100 mg L−1, H2O2 concentration = 3 wt%, temperature = 30 °C and pH = 9, the Co0.5Cu0.5O catalyst could completely degrade the Congo red within 60 min. The degradation products were analyzed by a liquid chromatography-mass spectrometer and the degradation pathway was revealed. To investigate the catalytic mechanism, the pH and concentrations of H2O2 and metal ions were monitored during the Fenton process. Mechanistic studies revealed that hydroxyl radicals and superoxide radicals derived from the activation of H2O2 molecules by metal centers were mainly responsible for the degradation of Congo red, and that copper ions played a critical role in the superior catalytic performance of the Co0.5Cu0.5O catalyst. The Co0.5Cu0.5O catalyst showed negligible metal leaching and outstanding recyclability, which are highly favorable for the practical application in the Fenton process.
Co-reporter:Yi Shen, Aik Chong Lua
International Journal of Hydrogen Energy 2015 Volume 40(Issue 1) pp:311-321
Publication Date(Web):5 January 2015
DOI:10.1016/j.ijhydene.2014.10.071
•Ni–Cu catalysts were synthesized using polyol reduction method for hydrogen production.•Dependence of synthesis conditions for the catalytic activity was studied.•The Ni–Cu/CNT catalyst showed excellent catalytic activity for methane decomposition.•A methane conversion of 0.8 and a carbon yield of 616 g C per g Ni were achieved.A series of nickel–copper nanoparticles were synthesized using the polyol reduction method and examined as catalysts for hydrogen production by methane decomposition. The effects of surfactant polyvinylpyrrolidone (PVP), carbon nanotube (CNT) support and heterogeneous nucleation seed, i.e., H2PtCl4 solution on the structural and catalytic properties of the resulting catalysts were studied. The catalysts were extensively characterized using field scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and N2 adsorption–desorption tests. The catalytic performance of the catalysts was evaluated in terms of methane conversion and carbon yield. It was found that the Ni–Cu alloying degree in the catalyst was critical to achieve high activity and that the catalytic performance was also closely related to the CNT support, the size and dispersion of the Ni–Cu particles. Among the catalysts, the Ni–Cu/CNT catalyst synthesized in the presence of PVP and H2PtCl4 solution exhibits the best catalytic activity with a stable methane conversion value of 0.8 and a carbon yield of 616 g C gNi−1 at 700 °C. The structures of the produced carbon materials were also characterized. Filamentous carbon nanofibers were obtained from the catalysts with high Ni–Cu alloying degrees while limited carbon lumps were generated from the catalyst with a low Ni–Cu alloying degree.
Co-reporter:Ling Zhang ;Dr. Yi Shen
ChemElectroChem 2015 Volume 2( Issue 6) pp:887-895
Publication Date(Web):
DOI:10.1002/celc.201402432
Abstract
A three-component platinum–ceria/graphene nanosheet hybrid (Pt–CeO2−x/GNS) was prepared through a facile one-pot synthesis method and examined as an electrocatalysts for alcohol (methanol, ethanol, ethylene glycol, and glycerol) oxidation. The structures of the catalysts were characterized by using transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). It was found that ultrafine Pt particles were intimately deposited at the interface of the CeO2−x and GNS support, resulting in the formation of abundant Pt–CeO2−x/GNS triple junctions in the hybrid. XPS results indicated a strong metal–support interaction in the catalyst. It was demonstrated that Pt–CeO2−x/GNS showed superior catalytic performance in comparison with the Pt/GNS catalyst. The superior catalytic performance of the Pt–CeO2−x/GNS catalyst was attributed to the presence of Pt–CeO2−x/GNS triple junctions, which facilitated the synergistic effects of the constituents.
Co-reporter:Yi Shen, Zhihui Zhang, Ranran Long, Kaijun Xiao, and Jingyu Xi
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 17) pp:15162
Publication Date(Web):August 21, 2014
DOI:10.1021/am503309h
In this study, the pristine graphene nanosheets (GNS) derived from chemical vapor deposition process were employed as catalyst support. In spite of the extremely hydrophobic GNS surface, ultrafine Pt nanoparticles (NPs) were successfully assembled on the GNS through a surfactant-free solution process. The evolution of Pt NPs in the GNS support was studied using transmission electron microscopy. It was found that the high-energy surface sites in the GNS, such as edges and defects, played a critical role on anchoring and stabilizing Pt nuclei, leading to the formation of Pt NPs on the GNS support. The concentration of the Pt precursor, i.e., H2PtCl6 solution had significant effects on the morphology of Pt/GNS hybrids. The resulting Pt/GNS hybrids were examined as catalysts for methanol electro-oxidation. It was indicated that the electrochemical active surface area and catalytic activity of the Pt/GNS hybrids were highly dependent on Pt loadings. The superior activity of the catalysts with low Pt loadings was attributed to the presence of Pt subnanoclusters as well as the strong chemical interaction of Pt NPs with the GNS support.Keywords: catalyst support effects; direct methanol fuel cells; electro-catalysts; graphene nanosheets; polyol-assisted synthesis; Pt ultrafine nanoparticles
Co-reporter:Yi Shen, Zhihui Zhang, Kaijun Xiao and Jingyu Xi
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 39) pp:21609-21614
Publication Date(Web):2014/08/29
DOI:10.1039/C4CP03048F
Downsizing the Pt particle to the atomic level in the electro-catalysts is highly desirable to enhance its utilization efficiency in fuel cells. In this study, Pt subnano/nanoclusters were stabilized by the pristine graphene nanosheets (GNSs) derived from chemical vapor deposition and the resulting Pt/GNS hybrids were examined as catalysts for electro-oxidation of alcohols (methanol, ethanol, ethylene glycol and glycerol). In spite of the strong hydrophobic surface, the GNS was proved to be a promising catalyst support because the edges and defects in the GNS could effectively anchor and stabilize the Pt subnano/nanoclusters. The Pt/GNS catalyst showed an extremely high electrochemical active surface area and superior catalytic activity for alcohol oxidation compared with the commercial Pt/carbon black catalyst. The enhanced catalytic performance was attributed to the presence of the discrete Pt subnano/nanoclusters as well as the modulation of the electronic properties of Pt nanoparticles through the chemical interaction of Pt atoms with the edges and defects of the GNS support.
Co-reporter:Dr. Yi Shen;Mr. Zhihui Zhang; Kaijun Xiao; Jingyu Xi
ChemCatChem 2014 Volume 6( Issue 11) pp:3254-3261
Publication Date(Web):
DOI:10.1002/cctc.201402629
Abstract
Ultrafine Pt, PtRh, and PtRhNi particles were assembled on pristine graphene nanosheets (GNSs), and the resulting hybrids were examined as electrocatalysts for ethanol oxidation. The structures of the catalysts were characterized by using transmission electron microscopy and X-ray diffraction. The bulk composition of the catalysts was determined by using energy-dispersive X-ray spectroscopy, and the surface composition of the nanoparticles was analyzed by using X-ray photoelectron spectroscopy. The activity of the catalysts for ethanol electrooxidation was studied by using cyclic voltammetry, linear sweeping voltammetry, and chronoamperometry. The activity of the catalysts followed the order of Pt/GNS<PtRh/GNS<PtRhNi/GNS, and it was well correlated with the structural characteristics of the catalysts. The excellent activity and stability of the PtRhNi/GNS catalyst was attributed to the bifunctional effects as well as the modification of Pt electronic structures.
Co-reporter:Yi Shen, Yongfang Zhou, Bin Gong, Kaijun Xiao, Lei Wang, Jingyu Xi
Journal of Catalysis (January 2017) Volume 345() pp:70-77
Publication Date(Web):1 January 2017
DOI:10.1016/j.jcat.2016.11.024
•Decahedral platinum crystals were synthesized in the presence of graphite nanosheets.•Pt decahedra decorated graphene nanosheets show outstanding performance for FAO.•The superior activity is well correlated with the unique structures of Pt decahedra.Synthesis of five-twined platinum decahedra is currently a great challenge. Reported herein is a solution synthesis of ultrafine decahedral platinum crystals (average size 5.9 nm) mediated by graphite nanosheets together with poly (dimethyl diallyl ammonium chloride). The graphite nanosheets play a critical role in the formation of Pt decahedra. The obtained Pt decahedral crystals provide a valuable platform for the fundamental study of facet-dependent activity of platinum. The hybrid of Pt decahedral crystal decorated graphite nanosheets shows outstanding activity and durability for the oxidation of formic acid. The hybrid possesses a remarkable current density of 4.3 mA cm−2, which is 2 times that of state-of-the-art Pt/C catalyst. The superior catalytic performance is well correlated with the unique structures of decahedral Pt crystals. The synthesis protocol disclosed in this study would pave a new route to fabricate high-performance electrocatalysts for fuel cells.Download high-res image (132KB)Download full-size image
Co-reporter:Yi Shen, Zhihui Zhang, Kaijun Xiao and Jingyu Xi
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 39) pp:NaN21614-21614
Publication Date(Web):2014/08/29
DOI:10.1039/C4CP03048F
Downsizing the Pt particle to the atomic level in the electro-catalysts is highly desirable to enhance its utilization efficiency in fuel cells. In this study, Pt subnano/nanoclusters were stabilized by the pristine graphene nanosheets (GNSs) derived from chemical vapor deposition and the resulting Pt/GNS hybrids were examined as catalysts for electro-oxidation of alcohols (methanol, ethanol, ethylene glycol and glycerol). In spite of the strong hydrophobic surface, the GNS was proved to be a promising catalyst support because the edges and defects in the GNS could effectively anchor and stabilize the Pt subnano/nanoclusters. The Pt/GNS catalyst showed an extremely high electrochemical active surface area and superior catalytic activity for alcohol oxidation compared with the commercial Pt/carbon black catalyst. The enhanced catalytic performance was attributed to the presence of the discrete Pt subnano/nanoclusters as well as the modulation of the electronic properties of Pt nanoparticles through the chemical interaction of Pt atoms with the edges and defects of the GNS support.
Co-reporter:Yi Shen, Ling Li, Jingyu Xi and Xinping Qiu
Journal of Materials Chemistry A 2016 - vol. 4(Issue 16) pp:NaN5822-5822
Publication Date(Web):2016/03/17
DOI:10.1039/C6TA01236A
We report a novel three-dimensional architecture, consisting of tungsten carbide nanocrystals which are intimately riveted to graphite felt fabrics by carbon nanosheets (CNS@WC/GF). The as-prepared CNS@WC/GF monolith is utilized as a binder-free hydrogen evolution reaction electrode in both acidic and alkaline solutions. It demonstrates remarkable activity as well as durability.
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