Defect-Modified Ultrathin BiOX (X = Cl, Br) Nanosheets Via a Top–Down Approach with Effective Visible-Light Photocatalytic Degradation

Resizing and engineering defects of two-dimensional (2D) layered semiconductors is of considerable importance for improving their photocatalytic performance. We, herein, report first a top–down strategy for synthesizing ultrathin BiOX (X = Cl, Br) nanosheets (NSs) with reducing size and engineering surface oxygen vacancies simultaneously, which is known as laser irradiation in liquid technique. The oxygen vacancies are spontaneously introduced during the regrowth of broken BiOX molecules and ions into ultrathin nanosheets. The electronic structure calculations reveal the alteration of the electronic structure induced by surface oxygen vacancies, which is well consistent with UV–vis absorption spectra. The further formation energy calculations suggest that the surface oxygen vacancies are abundant even under an O-rich condition. Importantly, the engineered ultrathin BiOX NSs exhibit excellent visible-light photocatalytic performances on the degradation of rhodamine B (RhB). Detailed investigations attribute the excellent performance mainly to the surface oxygen vacancies. On the one hand, it captures O 2 molecules as reactive oxygen species ( • O 2 – ). On the other hand, it modulates the electronic structure of ultrathin BiOX NSs, leading to the promotion of visible-light absorption and enhancement of the oxidation ability of holes. Our strategy opens up a new pathway to engineer structures and defects of 2D layered nanomaterials, which, in turn, could encourage potential applications.