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.
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