Band structure and photocatalytic activities for H2 production of ABi2Nb2O9 (A = Ca, Sr, Ba)

A new series of layered perovskite photocatalysts, ABi2Nb2O9 (A = Ca, Sr, Ba), were synthesized by the conventional solid-state reaction method and characterized by X-ray diffraction (XRD) and UV-visible spectrometer. The results showed that the structure of ABi2Nb2O9 (A = Ca, Sr) is orthorhombic, while that of BaBi2Nb2O9 is tetragonal. The band gaps of CaBi2Nb2O9, SrBi2Nb2O9, and BaBi2Nb2O9 were estimated to be 3.46, 3.43, and 3.30 eV, respectively. It was found from the electronic band structure study, using the density functional theory (DFT) with planewave basis, that the conduction bands of these photocatalysts mainly consist of Nb 4d + Bi 6p + O 2p orbitals and the valence bands are composed of hybridization with O 2p + Nb 4d + Bi 6s orbitals. The photocatalytic activities for water splitting were investigated under UV-light irradiation and indicated that these photocatalysts showed photocatalytic activity for H2 and O2 evolution from aqueous solutions containing sacrificial reagents (methanol and Ag+).