Surface states modulation via vacancy engineering for creating band bending on semiconductor BiOBr photocatalysts

Abstract

In microelectronic devices, surface modification could be used to introduce acceptor or donor surface states by defect engineering method to modify the alignment of energy band for desired properties, which was not used in the catalytic performance enhancement of powder photocatalysts. In this work, surface oxygen vacancies are induced to adjust the surface electrical structures and characteristics of the semiconductor bismuth oxybromide (BiOBr). In addition to being defect states to trap photoexcited electrons, surface oxygen vacancies also bring acceptor surface states, which result in an enhanced upward band bending and attract more photoexcited holes to the surface. Significantly, with a high concentration of electrons and holes accumulated on the surface, the BiOBr with surface oxygen vacancies shows good activity in the activation of O2 and oxidation of water compared to the one with bulk oxygen vacancies. Especially, it can decompose Rhodamine B (RhB) under natural sunlight in one minute, exceeding the majority of previously reported photocatalytic materials under comparable conditions. This work demonstrates that the surface oxygen vacancies could induce strengthened band bending at the BiOBr surface and remarkably improve catalytic performance, which provides a scalable strategy to practically manipulate the surface built-in electric field of powder photocatalysts.