Recent progress on design and applications of transition metal chalcogenide-associated electrocatalysts for the overall water splitting

Electrochemical hydrogen evolution via water splitting has been regarded as a highly promising technique for fossil-fuel substitution in the future to avoid environmental pollution and energy waste. As half of the water splitting reaction, the oxygen evolution reaction (OER) is the major obstacle because of the sluggish kinetics of the complex reaction. It is imperative and urgent to develop highly efficient, low cost and earth-abundant electrocatalysts to overcome the sluggish kinetics issue. Among the various non-noble-metal-based electrocatalysts, transition metal chalcogenide (TMS) associated materials have been exploited as potential candidates for the past few years due to their excellent electrochemical performance and unique internal structure. In this review, we have summarized the recent advances of transition metal sulfides (TMSs) for hydrogen evolution reaction (HER), OER, and overall water splitting, then we have reviewed several modified strategies from the perspective of their functional concepts to synthesis methods, characterization techniques, catalytic mechanisms and performances. Finally, the existing deficiencies, challenges and future development directions of TMSs in OER, HER, and overall water splitting process are further discussed and summarized.