Solar Water Splitting Using Powdered Photocatalysts Driven by Z-Schematic Interparticle Electron Transfer without an Electron Mediator

Abstract

Ru/SrTiO 3:Rh photocatalyst powder for H 2 evolution and varied photocatalyst powders for O 2 evolution such as BiVO 4 and WO 3 were suspended in acidified aqueous solutions, resulting in showing activities for water splitting into H 2 and O 2 in a stoichiometric ratio without an electron mediator under visible light irradiation. The photocatalytic activities were dependent on pH. The highest activity was obtained at pH 3.5. An optical microscope observation of the aqueous suspension containing Ru/SrTiO 3:Rh and BiVO 4 powders at pH 3.5 revealed that these powders aggregated with suitable contact. The condition of Rh doped in SrTiO 3 also affected strongly the photocatalytic activity and quenching of the photoluminescence of BiVO 4 . The high photocatalytic activity was obtained and the luminescence was remarkably quenched, when SrTiO 3:Rh containing Rh species with reversible redox properties was used and mixed. These results indicated that the photocatalytic water splitting and quenching of the photoluminescence occurred through interparticle electron transfer from the conduction band of BiVO 4 to impurity level consisting of the reversible Rh species doped in SrTiO 3 . Thus, we succeeded in constructing unique and simple Z-scheme photocatalysis systems driven by interparticle electron transfer under visible light irradiation. In addition, the (Ru/SrTiO 3:Rh)−(BiVO 4 ) system split water under simulated sunlight (AM-1.5).