Recent advances and the design criteria of metal sulfide photocathodes and photoanodes for photoelectrocatalysis

Metal sulfides have emerged as promising materials for photoelectrochemical (PEC) applications due to their favorable light absorption ability, tunable structural and optical properties. With the rapid development of PEC systems, an increasing number of studies have successfully designed high-performing metal sulfide photoelectrodes. Given the tunability of p-type and n-type behaviors of metal sulfides, they have been extensively employed as both photocathodes and/or photoanodes in a PEC system. While metal sulfides have been demonstrated to be a good photoabsorber, some studies have constructed sulfide-based composite photoelectrodes to further improve the charge transfer and consumption capabilities. In this review, we focus on assessing recent publications that used metal sulfide photoelectrodes for PEC applications, with the aim of evaluating the vital parameters required for the design of metal sulfide photocathodes and photoanodes. Detailed discussions of various metal sulfide photocathodes and photoanodes used for PEC applications are provided. Apart from the most commonly used binary metal sulfides (CdS, MoS₂and ZnS), ternary and quaternary metal sulfides (including the recently explored ZnIn₂S₄, Cu₂ZnSnS₄and CuInGaS₂) will also be reviewed thoroughly. More importantly, we summarize the key design strategies to design a high-performing metal sulfide photoelectrode by providing an overview of the design criteria as well as highlighting the main differences in fabricating metal sulfide photocathodes and photoanodes.