Cu doping enhanced ZnIn2S4/TiO2(VO) Z-scheme heterojunction for efficient photocatalytic overall water splitting

The design and synthesis of efficient photocatalysts for overall water splitting is a promising research topic. By reasonable modification, the hydrogen evolution photocatalyst can have the ability for overall water splitting. Both ZnIn2S4 and TiO2 have shown great potential in the field of photocatalytic hydrogen evolution, but their use for efficient overall water splitting is challenging. In this work, a Z-scheme heterojunction material of Cu-doped ZnIn2S4 composite TiO2 with rich oxygen vacancies was synthesized. Cu doping enhanced the light absorption, reduced the bandgap, and improved photocatalytic activity. In addition, the oxygen vacancies in TiO2 were conducive to the separation and migration of electron-hole pairs, and the construction of a Z-scheme heterojunction between ZnIn2S4 and TiO2 can also effectively promote the separation and migration of carriers. Therefore, the photocatalytic activity of this material was significantly improved and exhibited excellent overall water splitting activity without any sacrificial agents and co-catalysts. The optimized hydrogen and oxygen evolution rates were 589.64 μmol/g/h and 292.75 μmol/g/h, respectively. This work provided favorable evidence for metal element doping to promote the photocatalytic activity of composite heterojunction materials and provided a new strategy for the development of heterojunction photocatalysts for overall water splitting.