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Du J.,Key Laboratory of Advanced Energy Materials Chemistry | Chen C.,Key Laboratory of Advanced Energy Materials Chemistry | Cheng F.,Key Laboratory of Advanced Energy Materials Chemistry | Chen J.,Key Laboratory of Advanced Energy Materials Chemistry | Chen J.,Nankai University
Inorganic Chemistry | Year: 2015

Transition-metal oxides have attracted extensive interest as oxygen-reduction/evolution reaction (ORR/OER) catalyst alternatives to precious Pt-based materials but generally exhibit limited electrocatalytic performance due to their large overpotential and low specific activity. We here report a rapid synthesis of spinel-type CoMn2O4 nanodots (NDs, below 3 nm) monodispersed on graphene for highly efficient electrocatalytic ORR/OER in 0.1 M KOH solution. The preparation of the composite involves the reaction of manganese and cobalt salts in mixed surfactant-solvent-water solution at mild temperature (120 °C) and air. CoMn2O4 NDs homogeneously distributed on carbonaceous substrates show strong coupling and facile charge transfer. Remarkably, graphene-supported CoMn2O4 NDs showed 20 mV higher ORR half-wave potential, twice the kinetic current, and better catalytic durability compared to the benchmark carbon-supported Pt nanoparticles (Pt/C). Moreover, CoMn2O4/reduced graphene oxide afforded electrocatalytic OER with a current density of 10 mA cm-2 at a low potential of 1.54 V and a small Tafel slope of ∼ 56 mV/dec. This indicates that the composite of CoMn2O4 nanodots monodispersed on graphene is promising as highly efficient bifunctional electrocatalysts of ORR and OER that can be used in the areas of fuel cells and rechargeable metal-air batteries. © 2015 American Chemical Society. Source

Liu J.,Shanxi Datong University | LU C.,Shanxi Datong University | LU C.,Key Laboratory of Advanced Energy Materials Chemistry | Jin C.,Shanxi Datong University | And 2 more authors.
Chemical Research in Chinese Universities | Year: 2016

Periodic density functional theory(DFT) calculations are presented to describe the adsorption and decomposition of CH3OH on Ru(0001) surfaces with different coverages, including p(3×2), p(2×2), and p(2×1) unit cells, corresponding to monolayer(ML) coverages of 1/6, 1/4, and 1/2, respectively. The geometries and energies of all species involved in methanol dissociation were analyzed, and the initial decomposition reactions of methanol and the subsequent dehydrogenations reactions of CH3O and CH2OH were all computed at 1/2, 1/4, and 1/6 ML coverage on the Ru(0001) surface. The results show that coverage exerts some effects on the stable adsorption of CH3O, CH2OH, and CH3, that is, the lower the coverage, the stronger the adsorption. Coverage also exerts effects on the initial decomposition of methanol. C—H bond breakage is favored at 1/2 ML, whereas C—H and O—H bond cleavages are preferred at 1/4 and 1/6 ML on the Ru(0001) surface, respectively. At 1/4 ML coverage on the Ru(0001) surface, the overall reaction mechanism can be written as 9CH3OH→3CH3O+6CH2OH+9H→6CH2O+3CHOH+18H→ 7CHO+COH+CH+OH+26H→8CO+C+O+36H. © 2016, Jilin University, The Editorial Department of Chemical Research in Chinese Universities and Springer-Verlag GmbH. Source

Wang L.,Shandong University | Wang L.,Nankai University | Gu W.,Nankai University | Gu W.,Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry | And 8 more authors.
Zeitschrift fur Anorganische und Allgemeine Chemie | Year: 2012

Solvothermal combination of trivalent lanthanide metal precursors with 1, 2, 4, 5-cyclohexanetetracarboxylic acid (L) ligand has afforded the preparation of a family of eight new coordination polymers [Ln 4(L) 3(H 2O) 10]·7H 2O (Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) (1-8). Structural analyses reveal that the 1, 2, 4, 5-cyclohexanetetracarboxylic acid ligand with e,a,a,e (L I) conformation displays a μ 4-(κ 3O, O, O 5)(κ 2O 2,O 2) (κ 2O 4,O 4)-bridging mode to generate 3D frameworks of complexes 1-8 and the α-Po topology with the short Schläfli symbol {4 12.6 3} could be observed in complexes 1-8. The near-infrared luminescence properties were studied, and the results have shown that the Ho III, Er III, and Yb III complexes emit typical near-infrared luminescence in the solid-state. Variable-temperature magnetic susceptibility measurements of complexes 2-7 have shown that complex 2 (Gd) shows the ferromagnetic coupling between magnetic centers, whereas the complexes 3-7 show the antiferromagnetic coupling between magnetic centers. Additionally, the thermogravimetric analyses were discussed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Xiang X.,Key Laboratory of Advanced Energy Materials Chemistry | Xiang X.,Nankai University | Zhang K.,Key Laboratory of Advanced Energy Materials Chemistry | Zhang K.,Nankai University | And 2 more authors.
Advanced Materials | Year: 2015

Sodium-ion batteries (SIBs) receive significant attention for electrochemical energy storage and conversion owing to their wide availability and the low cost of Na resources. However, SIBs face challenges of low specific energy, short cycling life, and insufficient specific power, owing to the heavy mass and large radius of Na+ ions. As an important component of SIBs, cathode materials have a significant effect on the SIB electrochemical performance. The most recent advances and prospects of inorganic and organic cathode materials are summarized here. Among current cathode materials, layered transition-metal oxides achieve high specific energies around 600 mW h g-1 owing to their high specific capacities of 180-220 mA h g-1 and their moderate operating potentials of 2.7-3.2 V (vs Na+/Na). Porous Na3V2(PO4)3/C nanomaterials exhibit excellent cycling performance with almost 100% retention over 1000 cycles owing to their robust structural framework. Recent emerging cathode materials, such as amorphous NaFePO4 and pteridine derivatives show interesting electrochemical properties and attractive prospects for application in SIBs. Future work should focus on strategies to enhance the overall performance of cathode materials in terms of specific energy, cycling life, and rate capability with cationic doping, anionic substitution, morphology fabrication, and electrolyte matching. Various inorganic and organic compounds are being studied as cathode materials of sodium-ion batteries (SIBs), which mainly cover transition-metal oxides, polyanionic compounds, metal hexacyanometalates, aromatic carbonyl compounds, pteridine derivatives, and functional polymers. Currently, layered transition-metal oxides are most promising for application in SIBs owing to their high specific energies and the large space of promoting cycling life and rate capability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Zhang C.,Nankai University | Zhang C.,Key Laboratory of Advanced Energy Materials Chemistry | Liang X.,Nankai University | Liang X.,Key Laboratory of Advanced Energy Materials Chemistry | And 2 more authors.
International Journal of Hydrogen Energy | Year: 2011

Pyrolytic waste tire char was modified to be used as support and a series of catalysts supported with 0.1-1.0 wt% Pt were prepared by conventional wetness impregnation method. TEM images show that the Pt nanoparticles are well-dispersed in any microregions in the sample view on the TEM grid. The results of methylcyclohexane dehydrogenation reaction show the Pt loadings and the reaction temperature have a significant impact on the catalytic activity. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source

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