Understanding the photocatalytic mechanisms of the BiOBr/BiOCl heterostructures: First-principles study

Bismuth oxyhalide is gradually becoming an important type of photocatalytic material due to its high light responsiveness in a wide range of visible light. Among these materials, BiOCl with an indirect band gap greater than 3eV cannot respond under visible light, which limits its practical application; while BiOBr can respond to visible light, but its response intensity is low. Therefore, in this work, we constructed bulk BiOCl, BiOCl slab, bulk BiOBr, BiOBr slab and BiOBr/BiOCl heterojunction models based on density functional theory, and conducted detailed theoretical calculations to understand the electronic properties, charge transfer and optical properties of BiOBr/BiOCl heterojunctions. The results show that the charge transfer mechanism of BiOBr/BiOCl conforms to the type II heterostructure; the existence of the built-in electric field in the BiOBr/BiOCl heterostructure can promote the separation of photogenerated electron-hole pairs; BiOBr/BiOCl enhanced the light absorption properties of pure BiOCl. In summary, BiOBr/BiOCl can improve the photocatalytic performance of BiOCl.