Synthesis of BiOBr/WO3 p-n heterojunctions with enhanced visible light photocatalytic activity

A prerequisite for the development of photocatalysis techniques is to obtain photocatalysts with remarkable activity. Herein, we have reported BiOBr/WO3 p-n heterojunctions as novel and efficient visible-light-driven photocatalysts. The BiOBr/WO3 p-n heterojunctions have been prepared through an electrospinning-calcination-solvothermal method, and they all present a flower-like superstructure. The photocatalytic activities of these p-n heterojunctions are investigated by degrading rhodamine B (RhB), methyl orange (MO) and para-chlorophenol (4-CP) under visible light irradiation (lambda > 400 nm), respectively. When RhB serves as the target pollutant, all BiOBr/WO3 p-n heterojunctions with different theoretical molar ratios of BiOBr and WO3 (1/0.5, 1/1, 1/2) exhibit higher photocatalytic activity than pure WO3 or BiOBr. Especially, the BiOBr/WO3 p-n heterojunction with a molar ratio of 1/1 displays the highest photocatalytic activity among all the as-synthesized catalysts, even higher than the activity from the mixture of two individual photocatalysts with the same weight of components (WO3 and BiOBr). In addition, when MO or 4-CP acts as the target pollutant, the BiOBr/WO3 p-n heterojunction with a molar ratio of 1/1 still exhibits excellent photocatalytic performance. Furthermore, the recycling experiment confirms that the BiOBr/WO3 p-n heterojunction is essentially stable during the photocatalytic process. The enhanced photocatalytic activity of the BiOBr/WO3 p-n heterojunction is predominantly attributed to the efficient separation of photo-generated electrons and holes. The photogenerated holes (h(+)) and superoxide radical anions (O-center dot(2)-) have been found to be the primary reactive species responsible for the nearly complete mineralization of RhB dye in water.