Visible-light-driven H2 production from heterostructured Zn0.5Cd0.5S–TiO2 photocatalysts modified with reduced graphene oxides

Abstract

Although, hydrogen is a promising green energy source, current catalysts for hydrogen production cannot use the full range of visible light. In addition, these catalysts suffer from problems such as rapid charge-carrier recombination. Therefore, a simple strategy to synthesize high-performance catalysts for visible-light-driven H₂ production is required. One promising method of increasing catalyst efficiency is the use of a heterojunction structure. Therefore, in this study, Zn_0.5Cd_0.5S–TiO₂ (ZCS–TiO₂) heterojunction photocatalysts were prepared via the controlled growth of Zn_0.5Cd_0.5S using a facile solvothermal method. The ZCS–TiO₂ heterojunction photocatalysts showed high hydrogen production performance from water upon exposure to visible light as a result of the increased separation of photogenerated charges. Based on this success, we further modified the surface of the Zn_0.5Cd_0.5S–TiO₂ catalyst with a reduced graphene oxide (RGO) cocatalyst to produce RGO/ZCS–TiO₂ composite heterojunction photocatalysts. These ternary composite heterojunction photocatalysts also showed good hydrogen production from water because of the enhanced electron transport endowed by RGO and the matching band structure between Zn_0.5Cd_0.5S and TiO₂. Furthermore, we investigated the effects of different loadings of RGO, as well as the use of physical mixtures, on the catalytic activity; the optimized 0.5%RGO/50%ZCS–TiO₂ composite exhibited distinctly greater photocatalytic activity than the 50%ZCS–TiO₂ and ZCS catalysts, as well as the 0.5%Pt/50%ZCS–TiO₂ catalyst. Thus, our study demonstrates a new approach for obtaining highly efficient ZCS-based photocatalysts.