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.