Construction of Rh,Ta-codoped BaTi₄O₉/Zn₂In₂S₅ S-scheme heterojunction for efficient visible-light-driven photocatalytic water splitting

Barium tetratitanate (BaTi₄O₉) with a pentagonal-prism tunnel structure is one kind of promising photocatalyst for hydrogen production via water splitting. However, its wide bandgap severely limits solar light absorption. In this study, Rh and Ta were co-doped into BaTi₄O₉ to narrow its bandgap. A Rh,Ta-BaTi₄O₉/Zn₂In₂S₅ composite was further constructed using an in situ solvothermal method. The density functional theory and in situ XPS characterization results confirmed that an S-scheme heterojunction formed at the interface between Rh,Ta-BaTi₄O₉ and Zn₂In₂S₅, which improved the solar light absorption and enhanced the separation efficiency of photogenerated charge carriers. The photocatalytic hydrogen evolution rate of the Rh,Ta-BaTi₄O₉/Zn₂In₂S₅ heterojunction reached 292.16 μmol g^-1 h^-1. This value was almost three times higher than that of pristine Zn₂In₂S₅. This work presents an efficient strategy for fabricating high-performance BaTi₄O₉-based photocatalysts through bandgap modulation and construction of S-scheme heterojunctions via metallic sulfide loading.