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

Abstract

A solid-state Z-scheme system is constructed whereby rutile titania (TiO2) and beta-iron disilicide (β-FeSi2) were combined to act as oxygen (O2)- and hydrogen (H2)-evolution photocatalysts, respectively, connected by gold (Au). β-FeSi2 island grains with diameters in the 0.5-2 μm range were formed on the surface of Au-coated TiO2 powder by the co-sputtering method. On the surface of TiO2 powder, the Au-Si liquidus phase was obtained via a Au-Si eutectic reaction, which contributed to the selective deposition and crystallization of β-FeSi2 island grains onto Au. After the loading of the H2-evolution cocatalysts platinum and chromium oxide onto β-FeSi2, the system obtained catalyzed the evolution of H2 and O2 in a stoichiometric ratio from pure water under ultraviolet light irradiation. The transfer of photoexcited electrons in the conduction band (CB) of β-FeSi2 to Pt causes the reduction of protons to H2, and the photogeneration of holes in the valence band (VB) of TiO2 causes the oxidation of water to O2. In addition, the photogenerated holes in the VB of β-FeSi2 and the photoexcited electrons in the CB of TiO2 combined with each other in the Au layer, affording the completion of the overall photocatalytic water-splitting.