A silver-inserted zinc rhodium oxide and bismuth vanadium oxide heterojunction photocatalyst for overall pure-water splitting under red light

Abstract

We have prepared a solid-state heterojunction photocatalyst, in which zinc rhodium oxide (ZnRh₂O₄) and bismuth vanadium oxide (Bi₄V₂O₁₁) as hydrogen (H₂) and oxygen (O₂) evolution photocatalysts, respectively, were connected with silver (Ag, ZnRh₂O₄/Ag/Bi₄V₂O₁₁). ZnRh₂O₄/Ag/Bi₄V₂O₁₁ was able to photocatalyze overall pure-water splitting under red-light irradiation with a wavelength of 700 nm. On the basis of the analogy with a solid-state heterojunction photocatalyst composed of ZnRh₂O₄, defective silver antimonate (Ag_1−xSbO_3−y), and Ag (R. Kobayashi et al., J. Phys. Chem. C, 2014, 118, 22450–22456), we consider that the overall water-splitting performance of the ZnRh₂O₄/Ag/Bi₄V₂O₁₁ photocatalyst was derived from the photoproduced holes that were generated in the valence band (VB) of Bi₄V₂O₁₁ contributing to O₂ liberation and the photoexcited electrons that were generated in the conduction band (CB) of ZnRh₂O₄ contributing to H₂ liberation. Importantly, Ag possibly acts as a solid-state electron mediator for the transfer of electrons from the CB of Bi₄V₂O₁₁ to the VB of ZnRh₂O₄.