Hybrid density functional studies for the effect of oxygen vacancy on the visible light photocatalytic activity in M (M=Li, Na, K, Rb, Cs)-doped [formula omitted]-Bi2O3

Abstract

In the work, the relative stability of the single substitutional defect MBi, single oxygen vacancy defect VO and the complex defect MBi-VO (M = Li, Na, K, Rb, Cs) in α-Bi2O3 as well as their influences on the electronic properties and optical absorption spectrum of α-Bi2O3 are investigated using hybrid density functional calculations. It is shown that the complex defect MBi-VO is easier to form than the single defect (MBi or VO). The calculated electronic structures and optical absorption spectrum for the supercell with complex defect are also closer to the available experimental data than these with the single defect. Further, the charge compensation effect in the M monodoped α-Bi2O3 case is supported. Particularly, the induced impurity level in the band gap by the single defect (MBi or VO) disappears when the complex defect MBi-VO is presented. This makes the possible recombination center of the photogenerated electrons and holes disappear. At the same time, the theoretical band gap in the complex defect case decreases, and the absorption capacity of the visible light enhances with increasing doping concentration. These calculations well understand the significant improvement of the photocatalytic activity in the visible light range for Na and Cs-dopedα-Bi2O3 in very recent experiments. Besides, it could be a good strategy to effectively improve the visible light photocatalytic activity of α-Bi2O3, by preparing α-Bi2O3 with oxygen vacancies.