Electronic structure and photocatalytic properties of ABi{sub 2}Ta{sub 2}O{sub 9} (A=Ca, Sr, Ba)

A new series of layered perovskite photocatalysts, ABi{sub 2}Ta{sub 2}O{sub 9} (A=Ca, Sr, 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{sub 2}Ta{sub 2}O{sub 9} (A=Ca, Sr) is orthorhombic, while that of BaBi{sub 2}Ta{sub 2}O{sub 9} is tetragonal. First-principles calculations of the electronic band structures and density of states (DOS) revealed that the conduction bands of these photocatalysts are mainly attributable to the Ta 5d+Bi 6p+O 2p orbitals, while their valence bands are composed of hybridization with O 2p+Ta 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{sub 2} evolution from an aqueous methanol solution is about 2.26 mmol h{sup -1} for the photocatalyst SrBi{sub 2}Ta{sub 2}O{sub 9}, which is much higher than that of CaBi{sub 2}Ta{sub 2}O{sub 9} and BaBi{sub 2}Ta{sub 2}O{sub 9}. The photocatalytic properties are discussed in close connection with the crystal structure and the electronic structure in details. - Graphical abstract: The valence band of the photocatalysts is consisted of O 2p, Ta 5d and Bi 6smore » orbitals and the conduction band is from Bi 6p, Ta 5d and O 2p orbitals. Photocatalytic properties of the photocatalyst for H{sub 2} evolution without using other co-catalysts from CH{sub 3}OH/H{sub 2}O solution and O{sub 2} evolution from AgNO{sub 3}/H{sub 2}O solution were observed under Hg lamp irradiation.« less