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Development of cost-effective, active and durable electrocatalysts for overall water splitting is still a huge challenge. Herein, we have constructed one-dimensional (1D) cobalt sulfide and vanadium sulfide heterojunction nanowires arranged on carbon cloth (Co9S8-V3S4/CC) as bifunctional electrocatalysts for the efficient overall water splitting. The 1D wire-structured Co9S8-V3S4 heterojunctions possess large surface area, plentiful active sites and rapid transport of electrons/reactants and the release of gas. Importantly, the electron transfer from Co9S8 to V3S4 occurs at the interface due to the strong electronic coupling effect in Co9S8-V3S4 heterojunction, in which the electron-attracting V3S4 (V2+) optimizes the adsorption of H* active species for hydrogen evolution reaction (HER), while the electron-losing Co9S8 (Co3+) responds to the enhancement of oxygen evolution reaction (OER) activity. Co9S8-V3S4/CC exhibits low overpotentials of 85 and 232 mV at 10 mA cm−2 and small Tafel slopes of 51 and 59 mV dec−1 for HER and OER, respectively. Especially, the electrolyzer with Co9S8 V3S4/CC as both the anode and cathode requires low onset voltage of 1.35 V and cell voltage of 1.53 V at 10 mA cm−2 and exhibits high Faradaic efficiencies and robust stability. It can be driven by a solar cell (1.53 V) for continuous production of hydrogen and oxygen. This study highlights the design of 1D sulfide heterojunction in pursuit of highly efficient electrocatalysts for overall water splitting.

The development of effective and low-cost catalysts for overall water splitting is essential for clean production of hydrogen from water. In this paper, we report the synthesis of cobalt-vanadium (Co-V) bimetal-based catalysts for the effective water splitting. The Co2V2O7· x H2O nanoplates containing both Co and V elements were selected as the precursors. After the calcination under NH3 atmosphere, the Co2VO4 and Co/VN could be obtained just by tuning the calcination temperature. Electrochemical tests indicated that the Co-V bimetal-based materials could be used as active hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalyst by regulating their structure. The Co/VN showed good performance for HER with the onset potential of 68 mV and can achieve a current density of 10 mA cm−2 at an overpotential of 92 mV . Meanwhile, the Co2VO4 exhibited the obvious OER performance with overpotential of 300 mV to achieve a current density of 10 mA cm−2. When the Co2VO4 and Co/VN were used as the anode and cathode in a two-electrode system, respectively, the cell needed a voltage of 1.65 V to achieve 10 mA cm−2 together with good stability. This work would be indicative to constructing Co-V bimetal-based catalysts for the catalytic application.