Electronic Optimization in V-Doped NiS Nanoarrays Enables High-Efficiency Sulfide Oxidation-Assisted Seawater Electrolysis

The combination of hydrogen production and sulfide degradation represents a promising approach for energy-saving seawater splitting while generating valuable sulfur. Herein, we show that V-doping can regulate the electronic structure of NiS, thus optimizing the reactants/intermediates' adsorption behaviors and reducing the corresponding energy barriers. Accordingly, for the sulfide oxidation reaction (SOR), the as-prepared catalyst needs a working potential of 0.62 V vs RHE to reach 100 mA cm^-2 accompanied by high robustness over 70 h. Besides, it can also trigger the hydrogen evolution reaction (HER) activity with a low overpotential of 0.196 V vs RHE at 10 mA cm^-2. By coupling the SOR and HER in alkaline seawater, the electrolyzer can yield 100 mA cm^-2 at 1.89 V, which is lower than that of conventional seawater splitting, significantly reducing the energy input. The formation of sulfur powder at the anode further confirms the economic feasibility of such a novel electrolysis system. This work shows an attractive attempt to construct outstanding NiS-based catalysts for sulfide degradation and simultaneous green hydrogen production.