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

Ru/SrTiO3:Rh photocatalyst powder for H2 evolution and varied photocatalyst powders for O2 evolution such as BiVO4 and WO3 were suspended in acidified aqueous solutions, resulting in showing activities for water splitting into H2 and O2 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/SrTiO3:Rh and BiVO4 powders at pH 3.5 revealed that these powders aggregated with suitable contact. The condition of Rh doped in SrTiO3 also affected strongly the photocatalytic activity and quenching of the photoluminescence of BiVO4. The high photocatalytic activity was obtained and the luminescence was remarkably quenched, when SrTiO3: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 BiVO4 to impurity level consisting of the reversible Rh species doped in SrTiO3. 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/SrTiO3:Rh)−(BiVO4) system split water under simulated sunlight (AM-1.5).