Construction of dual-Z-scheme WS2-WO3·H2O/g-C3N4 catalyst for photocatalytic H2 evolution under visible light

A dual-Z-scheme heterojunction consisting of WS2-WO3·H2O and g-C3N4-WO3·H2O was prepared through coupling partially oxidized WS2 with g-C3N4. The suitable band matching among WS2, WO3·H2O and g-C3N4 realize the directional separation of electrons and holes from g-C3N4 to WS2 and WO3·H2O respectively, and the holes of WS2 are also quenched with electrons of WO3·H2O in the WS2-WO3·H2O heterostructure. Thereby, photogenerated carrier recombination is efficiently suppressed, and a strong reducibility of WS2-WO3·H2O/g-C3N4 catalyst is stabilized. The WS2-WO3·H2O nanodots with a tight contact provide a short diffusion channel to facilitate the rapid migration of the g-C3N4 carriers from the vicinity of the cocatalyst to the target reaction sites, further, the active sites of WS2 edges are heavily exposed to improve the H2 evolution rate. Benefiting from such a dual-Z-scheme heterojunction, the optimized dual-Z-scheme WS2-WO3·H2O/g-C3N4 catalyst shows a high H2 evolution rate (1276.9 μmol h−1 g−1), which is 57 times higher than that of the original g-C3N4. This work raises a new design approach for heterostructure photocatalyst and provides a valuable reference for future research of photocatalytic H2 production.