A Mechanism Investigation of how the Alloying Effect Improves the Photocatalytic Nitrate Reduction Activity of Bismuth Oxyhalide Nanosheets

Abstract Alloyed bismuth oxyhalides have been widely used in photocatalytic water treatment processes due to their superior photocatalytic activity. However, there is no report on the removal of NO 3 − for alloyed bismuth oxyhalides, and the mechanism of the effect of alloying on NO 3 − reduction activity is still unclear. In this work, we prepared a series of BiOCl n Br 1‐n (0≤n≤1) with different Cl/Br ratios but with controlled similar morphologies, and explored their catalytic activities on reducing NO 3 − under visible light irradiation. Density functional theory investigations revealed that the formation energy for an oxygen (O) vacancy on the surface of BiOCl n Br 1‐n alloys is clearly reduced in comparison with the monohalide, illustrating that more O vacancies can be produced on the surface of BiOCl n Br 1‐n alloys. A high concentration of O vacancies not only promotes the adsorption of NO 3 − but also enhances the separation efficiency of the photogenerated electron‐hole (e–h) pairs, with both being beneficial to enhance the photocatalytic activity of BiOCl n Br 1‐n alloys for NO 3 − reduction. These new discoveries not only promote the design and development of new photocatalysts with excellent NO 3 − reduction properties, but also help to understand the relationship between alloying effects and semiconductor photocatalytic properties.