Z-Scheme Overall Water Splitting Using Zn<i><sub>x</sub></i>Cd<sub>1–<i>x</i></sub>Se Particles Coated with Metal Cyanoferrates as Hydrogen Evolution Photocatalysts
Yosuke Kageshima, Yui Gomyo, Hikaru Matsuoka, Hiroto Inuzuka, Hajime Suzuki, Ryu Abe, Katsuya Teshima, Kazunari Domen, Hiromasa Nishikiori
Abstract
Solid solutions of ZnSe and CdSe (ZnxCd1–xSe) exhibit intense visible-light absorption in the wavelength region from 480 to 750 nm, which can be tuned by adjusting the Zn/Cd ratio. These materials generated hydrogen from water containing [Fe(CN)6]4– as an electron donor after modification with a Pt cocatalyst. The surfaces of Pt/ZnxCd1–xSe specimens were shown to be coated with zinc and/or cadmium cyanoferrates during the photocatalytic reaction, resulting in stable hydrogen evolution. This layer of metal cyanoferrates is expected to promote the oxidation of [Fe(CN)6]4– and to protect the selenide photocatalysts against photocorrosion. A Z-scheme system consisting of the particulate Pt/Zn0.75Cd0.25Se and a CoOy/TaON photoanode combined with [Fe(CN)6]3–/4– as a redox mediator promoted overall water splitting under visible light. This is the first-ever demonstration of redox-mediated Z-scheme overall water splitting using selenide photocatalyst particles. The present study suggests the feasibility of using metal cyanoferrates to inhibit photocorrosion of group II metal selenide photocatalysts during Z-scheme water splitting.