Band gap tuning of Na₁ˍₓ Laₓ Ta₁ˍₓ Coₓ O₃ solid solutions for visible light photocatalysis

Monophase solid solutionsNa₁ˍₓLaₓTa₁ˍₓCoₓO₃ (x=0–0.25) were prepared with conventional solid state reactions method. The band gaps of the solid solutions can be tuned to effectively absorb visible light, with varying x value. The Na₀.₉La₀.₁Ta₀.₉Co₀.₁O₃ photocatalyst exhibited the highest performance of H₂ evolution (4.34μmol∕h) under visible light irradiation (λ>420nm), whereas no H₂ evolution is observed for NaTaO₃ under the same conditions. The first principles calculation using generalized gradient approximation revealed that the band gap alteration and the photocatalytic activities of Na₁ˍₓLaₓTa₁ˍₓCoₓO₃ are mainly due to the hybridization of Co 3d and O 2p orbitals.The work is supported by the JSPS fellowship and the Global Environment Research Fund from the MEXT of Japan