Mo-doped cobaltous sulfide nanosheet arrays as efficient catalysts for the sulfion oxidation reaction promoting hydrogen production with ultra-low electric energy consumption

Abstract

Constructing efficient coupling systems based on the hydrogen evolution reaction (HER) and the sulfion oxidation reaction (SOR) to realize low-cost hydrogen production could promote the rapid development of the hydrogen economy. However, sulfion is prone to poisoning the active site, leading to a decline in catalytic activity and inferior catalytic stability. Therefore, designing efficient and stable catalysts for the SOR and exploring the inherent reaction mechanism are still formidable challenges. Herein, nickel foam-supporting Mo-doped Co₃S₄ nanosheet arrays (Mo–Co–S/NF) are synthesized and exhibit robust SOR catalytic activity and high long-term durability. The doped Mo species greatly improves the electronic structure of active sites and then enhances the intrinsic activity of the SOR. Mo–Co–S/NF only requires an ultra-low potential of 0.294 V vs. RHE to achieve a current density of 100 mA cm⁻², which is significantly lower than that for the corresponding oxygen evolution reaction (OER, 1.610 V vs. RHE). What's more, Mo–Co–S/NF is further used to construct an asymmetric acid–base coupling electrolyzer based on the HER–SOR, which achieves simultaneous hydrogen and sulfur production with ultra-low energy consumption and can even generate extra electric energy at a low current density. This work provides unique insights into the design of SOR electrocatalysts and dissymmetrical electrolytes, providing more possibilities for green and low-cost hydrogen production.