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 α-Bi2O3

In the work, the relative stability of the single substitutional defect M-Bi, single oxygen vacancy defect V-O and the complex defect M-Bi-V-O (M = Li, Na, K, Rb, Cs) in alpha-Bi2O3 as well as their influences on the electronic properties and optical absorption spectrum of alpha-Bi2O3 are investigated using hybrid density functional calculations. It is shown that the complex defect M-Bi-V-O is easier to form than the single defect (M-Bi or V-O). 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 alpha-Bi2O3 case is supported. Particularly, the induced impurity level in the band gap by the single defect (M-Bi or V-O) disappears when the complex defect M-Bi-V-O 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-doped-alpha-Bi(2)O(3 )in very recent experiments. Besides, it could be a good strategy to effectively improve the visible light photocatalytic activity of alpha-Bi2O3, by preparing alpha-Bi2O3 with oxygen vacancies.