Developing cost-efficient electrocatalysts for oxygen evolution is vital for the viability of H2 energy generated via electrolytic water. Engineering favorable defects on the electrocatalysts to provide accessible act...Developing cost-efficient electrocatalysts for oxygen evolution is vital for the viability of H2 energy generated via electrolytic water. Engineering favorable defects on the electrocatalysts to provide accessible active sites can boost the sluggish reaction thermodynamics or kinetics. Herein, Col_xS nanosheets were designed and grown on reduced graphene oxide （rGO） by controlling the successive two-step hydrothermal reaction. A belt-like cobalt-based precursor was first formed with the assistance of ammonia and rGO, which were then sulfurized into Col_xS by L-cysteine at a higher hydrothermal temperature. Because of the non-stoichiometric defects and ultrathin sheet-like structure, additional cobalt vacancies （V^o） were formed/exposed on the catalyst surface, which expedited the charge diffusion and increased the electroactive surface in contact with the electrolyte. The resulting Col_xS/rGO hybrids exhibited an overpotential as low as 310 mV at 10 mA.cm-2 in an alkaline electrolyte for the oxygen evolution reaction （OER）. Density functional theory calculations indicated that the Vco on the Col_xS/rGO hybrid functioned as catalytic sites for enhanced OER. They also reduced the energy barrier for the transformation of intermediate oxygenated species, promoting the OER thermodynamics.展开更多
Cobalt molybdate/non-stoichiometric cobalt sulfide（CoMoO4/Co1-xS） hybrid was in situ grown on nickel foam by a simple two-step hydrothermal process. The as-prepared CoMoO4/Co1-xS hybrid electrode possessed core-shel...Cobalt molybdate/non-stoichiometric cobalt sulfide（CoMoO4/Co1-xS） hybrid was in situ grown on nickel foam by a simple two-step hydrothermal process. The as-prepared CoMoO4/Co1-xS hybrid electrode possessed core-shell nanostructure, large surface area and high specific capacitance of 2250 F g-1 at a current density of 1 A g-1. Using the hybrid as anode and activated carbon（AC） as cathode, an asymmetric supercapacitor of CoMoO4/Co1-xS//AC was fabricated. The optimized supercapacitor had large potential window of 1.6 V and high capacitance of 112 F g-1, resulting in high power density of 804.5 W kg-1 and energy density of 39.8 Wh kg-1. Furthermore, the supercapacitor exhibited an excellent long cycle life along with 86.4% specific capacitance retained after 5000 cycles. The superior performances and good stability of the asymmetric supercapacitor can be attributed to the unique structure of the two components in hybrid, and the positive synergistic effects of the hybrid electrodes. The facile preparation process and excellent performance presented here render the CoMoO4/Co1-xS hybrid as a promising candidate for energy storage device.展开更多
文摘Developing cost-efficient electrocatalysts for oxygen evolution is vital for the viability of H2 energy generated via electrolytic water. Engineering favorable defects on the electrocatalysts to provide accessible active sites can boost the sluggish reaction thermodynamics or kinetics. Herein, Col_xS nanosheets were designed and grown on reduced graphene oxide （rGO） by controlling the successive two-step hydrothermal reaction. A belt-like cobalt-based precursor was first formed with the assistance of ammonia and rGO, which were then sulfurized into Col_xS by L-cysteine at a higher hydrothermal temperature. Because of the non-stoichiometric defects and ultrathin sheet-like structure, additional cobalt vacancies （V^o） were formed/exposed on the catalyst surface, which expedited the charge diffusion and increased the electroactive surface in contact with the electrolyte. The resulting Col_xS/rGO hybrids exhibited an overpotential as low as 310 mV at 10 mA.cm-2 in an alkaline electrolyte for the oxygen evolution reaction （OER）. Density functional theory calculations indicated that the Vco on the Col_xS/rGO hybrid functioned as catalytic sites for enhanced OER. They also reduced the energy barrier for the transformation of intermediate oxygenated species, promoting the OER thermodynamics.
基金financial joint support by the National Natural Science Foundation of China (nos. 91422301, 51472094, 61474047)
文摘Cobalt molybdate/non-stoichiometric cobalt sulfide（CoMoO4/Co1-xS） hybrid was in situ grown on nickel foam by a simple two-step hydrothermal process. The as-prepared CoMoO4/Co1-xS hybrid electrode possessed core-shell nanostructure, large surface area and high specific capacitance of 2250 F g-1 at a current density of 1 A g-1. Using the hybrid as anode and activated carbon（AC） as cathode, an asymmetric supercapacitor of CoMoO4/Co1-xS//AC was fabricated. The optimized supercapacitor had large potential window of 1.6 V and high capacitance of 112 F g-1, resulting in high power density of 804.5 W kg-1 and energy density of 39.8 Wh kg-1. Furthermore, the supercapacitor exhibited an excellent long cycle life along with 86.4% specific capacitance retained after 5000 cycles. The superior performances and good stability of the asymmetric supercapacitor can be attributed to the unique structure of the two components in hybrid, and the positive synergistic effects of the hybrid electrodes. The facile preparation process and excellent performance presented here render the CoMoO4/Co1-xS hybrid as a promising candidate for energy storage device.
