Junction of ZnmIn2S3+m and bismuth vanadate as Z-scheme photocatalyst for enhanced hydrogen evolution activity: The role of interfacial interactions

A series of ZnmIn2S3+m photocatalysts were synthesized to show tunable band gap energy with the variation of Zn/S atomic ratio. The junction of ZnmIn2S3+m and BiVO4 led to intimate interfacial contacts. Both experimental and theoretical results implied that electrons flowed from ZnmIn2S3+m to BiVO4 at the ZnmIn2S3+m/BiVO4 interface to form built-in electric field due to the variation of Fermi level, which promised Z scheme charge transfer feature for improving separation of charge carriers for enhanced photocatalytic performance. A higher degree of charge transfer process occurred for Zn2In2S5/BiVO4 heterostructure promised stronger built-in electric field, higher charge separation efficiency and improved photocatalytic activity in comparison to ZnIn2S4/BiVO4 and Zn3In2S6/BiVO4 heterojunctions. The optimal hydrogen production rate of Zn2In2S5/BiVO4 photocatalyst is 8.42 mmol•g-1•h-1 with apparent quantum yield of 22.32 % at 435 nm, which is about 2.2 and 1.5 times higher than that of ZnIn2S4/BiVO4 and Zn3In2S6/BiVO4, respectively.