Z-Schematic CO₂ Reduction to CO through Interparticle Electron Transfer between SrTiO₃:Rh of a Reducing Photocatalyst and BiVO₄ of a Water Oxidation Photocatalyst under Visible Light

We have successfully constructed a Z-scheme system in a simple suspension system employing only metal oxide photocatalyst materials for CO2 reduction using water as an electron donor under visible light irradiation. The Z-scheme photocatalyst using SrTiO3:Rh as a reducing photocatalyst and BiVO4 as an O2-evolving photocatalyst working via interparticle electron transfer without electron mediators reduced CO2 to CO using water as an electron donor under visible light. Loading a Ag or Au cocatalyst on SrTiO3:Rh enhanced CO formation in the photocatalytic CO2 reduction and also photoelectrochemical CO2 reduction employing a SrTiO3:Rh photocathode. The suitable pH for Z-schematic CO2 reduction without electron mediators was 3.5–5 at which SrTiO3:Rh and BiVO4 particles aggregated well with each other, resulting in the achievement of Z-schematic CO2 reduction by efficient interparticle electron transfer. It is notable that the Z-schematic CO2 reduction proceeded using just photocatalyst powders, water, and CO2 because of self-pH-adjustment even without any additives inducing aggregation between SrTiO3:Rh and BiVO4 particles.