Surface-modified metal sulfides as stable H2-evolving photocatalysts in Z-scheme water splitting with a [Fe(CN)6]3-/4- redox mediator under visible-light irradiation

Z-scheme splitting of water into H-2 and O-2 was achieved using K-2[CdFe(CN)(6)]-modified metal sulfides as H-2-evolving photocatalysts combined with an appropriate O-2-evolution system (CoOx-loaded TaON photoanode) in the presence of [Fe(CN)(6)](3-/4-) as an electron mediator. Pt/CdS showed high activity (67.7 mu mol h(-1)) for H-2 evolution in borate buffer solution containing [Fe(CN)(6)](4-) as an electron donor under visible-light irradiation. A cyano complex containing [Fe(CN)(6)](4-) and Cd2+, which efficiently scavenged photogenerated holes and effectively facilitated the oxidation of [Fe(CN)(6)](4-) to [Fe(CN)(6)](3-), was formed on the CdS surface in the reaction. Modification of other metal sulfides, such as ZnIn2S4 and CdIn2S4, with the cyano complex K-2[CdFe(CN)(6)] significantly improved their rates of H-2 evolution (ZnIn2S4:4.8 -> 15 mu mol h(-1); CdIn2S4:0.8 -> 6 mu mol h(-1)) in the presence of [Fe(CN)(6)](4-) and an appropriate O-2-evolution system (CoOx-loaded TaON photoanode), enabling Z-scheme water splitting.