BiVO4-Ru/SrTiO3: Rh composite Z-scheme photocatalyst for solar water splitting

BiVO4-SrTiO3: Rh composites in which the Rh-doped SrTiO3 particles of a H-2-evolving photocatalyst attached on the BiVO4 particles of an O-2-evolving photocatalyst were prepared by an impregnation method and a liquid-solid state reaction. The composites showed photocatalytic activity for Z-schematic water splitting under visible light or simulated sunlight irradiation without an electron mediator. The optimum pH for the water splitting was neutral. Water splitting over the composite proceeded via an interparticle electron transfer from BiVO4 to Ru/SrTiO3: Rh particles at the large interfacial area obtained by those preparation methods. The photocatalytic water splitting activity of the composite depended on the crystallinity and morphology of BiVO4. The composite prepared by the liquid-solid state reaction showed the highest photocatalytic activity. This was due to the formation of well-crystallized BiVO4 single-crystal-like particles. The BiVO4-Ru/SrTiO3: Rh composite photocatalyst gave a quantum yield of 1.6% at 420 nm and a stable activity. Thus, we have developed the simplest system requiring no additives, except for photocatalyst powder and water, for photocatalytic solar water splitting.