Electronic structure and photocatalytic properties of ABi2Ta2O9 (A = Ca, Sr, Ba)

A new series of layered perovskite photocatalysts, ABi(2)Ta(2)O(9) (A = Ca, St. Ba), were synthesized by the conventional solid-state reaction method and the crystal structures were characterized by powder X-ray diffraction. The results showed that the structure of ABi(2)Ta(2)O(9) (A = Ca, Sr) is orthorhombic, while that of BaBi2Ta2O9 is tetragonal. First-principles calculations of the electronic bands structures and density of states (DOS) revealed that the conduction hands of these photocatalysts are mainly attributable to the Ta 5d+Bi 6p+O 2p orbitals, while their valence hands are composed of hybridization with O 2p+Ti 5d+Bi 6s orbitals. Photocatalytic activities for water splitting were investigated under UV light irradiation and indicated that these photocatalysts are highly active even Without co-catalysts. The formation rate of H-2 evolution from an aqueous methanol solution is about 2.26 mmol h(-1) for the photocatalyst SrBi2Ta2O9, which is much higher than that of CaBi2Ta2O9 and BaBi2Ta2O9. The photocatalytic properties are discussed in close connection with the crystal structure and the electronic Structure in details. (c) 2008 Elsevier Inc. All rights reserved.