Photocatalytic activities of rhodium and antimony-codoped SrTiO₃ (SrTiO₃:Sb/Rh) under visible light irradiation were investigated in order to develop new visible-light response oxide photocatalysts.
SrTiO₃:Sb/Rh was prepared by a hydrothermal synthesis. Photocatalytic reactions for H₂ evolution from an aqueous methanol solution (10 vol%) and for O₂ evolution from an aqueous silver nitrate solution (0.02 mol L^-1) were carried out in a gas-closed circulation system. A 300-W Xe lamp with attached cutoff filter was employed for visible light irradiation.
SrTiO₃:Sb/Rh showed new absorption bands in the visible light region in addition to the intrinsic absorption band due to band gap transition (Energy gap = 2.4 eV). Pt-loaded and IrO₂-loaded SrTiO₃:Sb/Rh showed photocatalytic activities for the H₂ evolution and the O₂ evolution under visible light irradiation, respectively. The visible-light response was due to charge transfer transition from electron donor levels formed by doped Rh³⁺ ions to the conduction band of the host. The photocatalytic activity of SrTiO₃:Sb/Rh strongly depended on the synthetic condition and the ratio of the Sb/Rh dopant. The synthetic condition and codoping of antimony affected the oxidation state and the environment around the doped rhodium species, and the surface active site of the SrTiO₃:Sb/Rh photocatalyst, resulting in that photocatalytic properties of SrTiO₃:Sb/Rh were improved.
It was found that SrTiO₃:Sb/Rh is a new oxide photocatalyst for H₂ and O₂ evolution from aqueous solutions containing sacrificial reagents under visible light irradiation.