Defect Physics of BiOI as High Efficient Photocatalyst Driven by Visible Light

Point defects are very important for semiconductor photocatalyst: promoting visible-light absorption, tailoring energy bands, trapping photogenerated carriers, etc. As promising high efficient photocatalyst, BiOI could absorb most solar energy, and has high oxidization activity. However, its conduction band edge is lower than the reduction potential of H+/H-2, thus BiOI could not achieve overall photocatalytic water splitting. In the present work, the crystal structure and electronic structure of BiOI with three different types of point defects are systematically investigated by density functional theory calculations, to find suitable strategy to solve above issue. Based on detailed analysis of calculated results, it is found that antisite defect of I@Bi (iodine occupies the bismuth site) and oxygen vacancy defect in BiOI could achieve above requirement: their conduction band and valence band edge positions are straddle the redox potential of water, resulting in as the promising photocatalyst candidates for overall water splitting driven by visible light. The findings could provide reasonable explanations for the reported experiments, and are beneficial to the development of novel bismuth oxyhalogenide-based photocatalyst.