Metal selenide photocatalysts for visible-light-driven Z-scheme pure water splitting

Abstract

Particulate metal selenides having narrow bandgaps for photocatalytic overall pure water splitting have not yet been reported due to the severe self-photooxidation of such materials. The present work demonstrates that solid solutions of zinc selenide and copper gallium selenide (ZnSe:CGSe), with absorption edges ranging from 480 to 750 nm, can be employed as H₂ evolution photocatalysts in particulate photocatalyst sheets for Z-scheme pure water splitting, where CoO_x/BiVO₄ and Au are used as the oxygen evolution photocatalyst and electron mediator, respectively. Photogenerated holes in the metal selenide are efficiently recombined with electrons from BiVO₄via the Au layer, thus avoiding self-oxidation of the selenides and leading to stable pure water splitting. Varying the ZnSe:CGSe composition demonstrates that both the p-type semiconductor character and excellent photoelectrochemical properties of selenides are vital to efficient Z-scheme water splitting. This study extends the application field of metal selenides in photocatalytic pure water splitting and creates new opportunities for selenide-based photocatalytic systems for solar fuel production.