Synthesis of Highly Active GaN:ZnO Photocatalysts Applicable to Z-Scheme Overall Water Splitting Systems

The Z-scheme system, integrating an oxygen evolution photocatalyst (OEP) with a hydrogen evolution photocatalyst (HEP), is an ideal strategy for photocatalytic overall water splitting (OWS), in which the development of an efficient OEP remains a challenge. Herein, the GaN:ZnO photocatalyst was synthesized by an ammonium halide-based process to perform a recorded apparent quantum yield of 30% at 420 nm for oxygen evolution from water. It made the GaN:ZnO a remarkable OEP for the construction of three distinct Z-scheme OWS systems, including an unbiased-photoelectrochemical sheet, direct collision, and redox-ion-mediated electron shuttle. The features and parameters of each Z-scheme system were discussed in relation to water splitting, and the most efficient one was established by employing [Fe(CN)6]3–/[Fe(CN)6]4– as an electron shuttle and SrTiO3:Rh as an HEP. This work not only provides a methodology for synthesizing an efficient GaN:ZnO photocatalyst but also highlights its great potential as an OEP applicable to constructing various Z-scheme OWS systems.