Designs of composite photocatalysts for their enhanced performance based on photoinduced charge transfer

Abstract

The author and coworkers focused on the fabrication of composite photocatalysts and charge transfer between composite constituents for increased activity and sensitivity to visible light, aiming at developing materials for environmental preservation through the oxidative decomposition of organic pollutants and clean energy production through water splitting for hydrogen generation. Cu2+ ion-grafted titanium dioxide (TiO2) was designed on the basis of visible-light-induced interfacial charge transfer from the valence band (VB) of TiO2 to Cu2+, generating high oxidative decomposition activity owing to the utilization of photogenerated holes in the VB of TiO2. Cu+ produced by electron injection was converted back to Cu2+ by oxygen (O2) reduction through multi-electron O2 reduction reaction. As for water splitting, zinc rhodium oxide (ZnRh2O4) and bismuth vanadate (Bi4V2O11) as H2 and O2 evolution photocatalysts, respectively, were connected with silver (Ag), acting as a solid-state electron mediator, to prepare a composite photocatalyst that is sensitive to red light. The key function of the heterojunction photocatalyst is the transfer of photoexcited electrons from the conduction band (CB) of Bi4V2O11 to the VB of ZnRh2O4 via Ag. Thus, the photoexcited electrons in the CB of ZnRh2O4 and the holes in the VB of Bi4V2O11 effectively reduced and oxidized water, respectively, thereby splitting water and liberating H2 and O2 at a stoichiometric ratio.