Band gap tuning of Na1−xLaxTa1−xCoxO3 solid solutions for visible light photocatalysis

Monophase solid solutions Na1−xLaxTa1−xCoxO3 (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 Na1−xLaxTa1−xCoxO3 are mainly due to the hybridization of Co 3d and O 2p orbitals.