Recent Advances in Transition Metal Sulfide Bifunctional Electrocatalysts for Overall Water Splitting

In response to the increasingly severe energy crisis and environmental pollution, electrocatalytic hydrogen production has been considered an ideal alternative to fossil fuels because of its sustainability, abundance, and zero emissions. Electrocatalytic water splitting includes two parts, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), and high-quality bifunctional electrocatalysts can avoid cross-effects between electrodes, simplify electrolyzer design, and reduce costs. Among them, transition metal sulfides (TMS) possess unique electronic orbital structures, two-dimensional characteristics, low cost, tunable electronic properties, and abundant active sites, showing great potential. This review introduces the HER/OER mechanisms in electrocatalytic water splitting and discusses key electrochemical parameters used to evaluate HER/OER performance. We systematically review the synthesis methods of three representative transition metal sulfide bifunctional catalysts, including hydrothermal, solvothermal, and electrodeposition methods, and summarize the strategies to improve catalyst performance by adjusting microstructure and electronic properties, with a focus on the structure-function relationship of the catalysts.