Metal selenides for photocatalytic Z-scheme pure water splitting mediated by reduced graphene oxide

Exploration of novel narrow bandgap semiconductors for overall water splitting is vital for the realization of practical solar H-2 production. In the work, solid solutions of zinc selenide and copper gallium selenide with absorption edge wavelengths ranging from 480 to 730 nm were developed. Using these metal selenides as H-2-evolving photocatalysts, CoOx/BiVO4 as the O-2-evolving photocatalyst, and reduced graphene oxide as the electron mediator, all-solid-state Z-scheme overall pure water splitting systems were constructed. The rate of photocatalytic H-2 evolution from aqueous solutions containing Na2S and Na2SO3 as the electron donors was evaluated while employing these selenide photocatalysts at various Zn/(Zn+Cu) and Ga/Cu molar ratios. The data demonstrate that efficient Z-scheme overall water splitting was significantly correlated to the photoelectrochemical performance of the selenide photocatalysts acting as photocathodes, rather than the photocatalytic activities of these materials during the sacrificial H-2 evolution. (C) 2019, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.