Formation of intermediate band and low recombination rate in ZnO-BiVO4 heterostructured photocatalyst: Investigation based on experimental and theoretical studies

We present systematic investigations on the relationship between interface formation and enhanced photocatalytic activity of ZnO-BiVO4 nanocomposite based on experimental techniques supported by theoretical calculations. The interaction between ZnO (101) nanosheet and BiVO4 surface at the heterojunction was explored to study the charge transfer and separation mechanism responsible for enhanced photocatalytic response. XPS results and DFT computations mutually validate the reasonable existence of ZnO-BiVO4 interface. The nanocomposite photocatalytic activity, tested for various weight ratios, was found to be highest for ZnO-BiVO4 (1 : 1) under visible-light irradiation. Moreover, the percentage removal of MB was found to be greater than RhB for the same time duration. Steady state and time resolve photoluminescence were employed to understand the carrier lifetime and emissivity. Visible light driven high photoactivity exhibited by ZnO-BiVO4 (1 : 1) was ascribed to the formation of intermediate band and comparatively low recombination rate, which facilitates the separation of electron-hole pairs. Based on the theoretical outcome, we found that valence band maximum was occupied by Bi s orbital and conduction band minimum was occupied by Zn s orbital, which indicates the maximum electron transition from BiVO4 valence band to ZnO conduction band in ZnO-BiVO4 composite. These results demonstrated that heterojunction semiconductors are an effective strategy that can be successfully applied to develop photocatalysts that respond to visible light for organic pollutant degradation.