A novel heterojunction BiOBr/bismuth oxyhydrate photocatalyst with highly enhanced visible light photocatalytic properties

In this study, a facile and effective method to modify the photocatalytic performance of a bismuth oxybromide (BiOBr) semiconductor through the fabrication of a heterojunction with a hydrated bismuth oxide (BHO) is reported. The new yBiOBr-(1 - y)BHO heterojunction, synthesized by a simple hydrothermal method, exhibits a high photocatalytic activity under visible light irradiation for the photodegradation of typical organic pollutants in water, such as Rhodamine B (RhB) and acetophenone (AP). Both the individual BiOBr and BHO components show very low photocatalytic efficiency. Furthermore, the unique photocatalytic performance of the new hybrid material was demonstrated through the uphill photocatalytic reaction that involves the oxidation of potassium iodide (KI) to triiodide. The remarkable photocatalytic activity of the coupled system is directly related to the effectual charge carrier separation due to the formation of the heterostructure. 0.9BiOBr-0.1BHO shows a higher photocatalytic activity as compared with other members of the same family, 0.8BiOCl-0.2BHO and 0.8BiOI-0.2BHO, which is directly ascribed to a synergistic effect of the energy band-gap structure and flow of charge carriers through the heterojunction, surface area, and light absorbance. In comparison with TiO ₂ (Degussa P25), the new composite material demonstrated 10.7 times higher activity in removing aqueous RhB under visible light (λ ≥ 420 nm) irradiation. Study of the photocatalytic mechanism proves that the degradation of RhB under visible light irradiation over the as-prepared 0.9BiOBr-0.1BHO is mainly via a direct hole oxidation mechanism and superoxide oxidation pathways. The resulting yBiOBr-(1 - y)BHO composites exhibit high photocatalytic and thermal stabilities and are very promising photocatalysts for degradation of organic pollutants in water and for other applications.