Conduction band tuning by strengthening s-p hybridization of novel layered oxyhalide Bi4SbO8Cl for efficient visible-light photocatalytic water splitting

Abstract

Bismuth-based Sillen–Aurivillius oxyhalide Bi4MO8Cl are promising visible-light photocatalysts. The element M of [MO4]3- perovskite layer in the Bi4MO8Cl is always a transition element. Due to d orbitals in transition element weakening the Bi 6s and O 2p orbitals hybridization, the bandgap energy would be decreased and the CBM would be lowered. Thus, Bi4MO8Cl always shows feeble reducibility for photocatalytic hydrogen generation. In this paper, we choose the main group element Sb substitute for transition element M in the Sillen–Aurivillius Bi4MO8Cl. Due to the s-p-d hybridization in Bi4NbO8Cl being replaced by only s-p hybridization in Bi4SbO8Cl, the strengthened Bi 6s and O 2p orbitals hybridization would eventually lead to the enlarged energy bandgap and elevated CBM. The bandgap of Bi4SbO8Cl was about 2.53 eV with the CBM estimated about −0.33 eV. Because of the high carrier mobility and strong reducibility brought by the dispersed Bi 6s states in the whole unoccupied states and the raised position of Bi 6p states in the CBM and linearity Sb–O–Sb, Bi4SbO8Cl shows enhanced photocatalytic H2 generation compared to Bi4NbO8Cl under the visible-light irradiation.