Synthesis of a Gold-Inserted Iron Disilicide and Rutile Titanium Dioxide Heterojunction Photocatalyst via the Vapor-Liquid-Solid Method and Its Water-Splitting Reaction.

A solid-state Z-scheme system is constructed whereby rutile titania (TiO) and beta-iron disilicide (β-FeSi) were combined to act as oxygen (O)- and hydrogen (H)-evolution photocatalysts, respectively, connected by gold (Au). β-FeSi island grains with diameters in the 0.5-2 μm range were formed on the surface of Au-coated TiO powder by the co-sputtering method. On the surface of TiO powder, the Au-Si liquidus phase was obtained via a Au-Si eutectic reaction, which contributed to the selective deposition and crystallization of β-FeSi island grains onto Au. After the loading of the H-evolution cocatalysts platinum and chromium oxide onto β-FeSi, the system obtained catalyzed the evolution of H and O in a stoichiometric ratio from pure water under ultraviolet light irradiation. The transfer of photoexcited electrons in the conduction band (CB) of β-FeSi to Pt causes the reduction of protons to H, and the photogeneration of holes in the valence band (VB) of TiO causes the oxidation of water to O. In addition, the photogenerated holes in the VB of β-FeSi and the photoexcited electrons in the CB of TiO combined with each other in the Au layer, affording the completion of the overall photocatalytic water-splitting.