Synthesis of a hierarchical BiOBr nanodots/Bi2WO6 p-n heterostructure with enhanced photoinduced electric and photocatalytic degradation performance

Three-dimensional composites of flower-like Bi2WO6 decorated with BiOBr nanodots (designated BiOBr nanodots/Bi2WO6) with varying BiOBr content have been prepared by a simple method. The BiOBr nanodots, with average diameters of 50 nm, adhered tightly to the surface of Bi2WO6 and formed p-n heterojunctions between BiOBr and Bi2WO6, as evidenced by the characterization of its structure and composition. Compared to pure Bi2WO6 and BiOBr, BiOBr/Bi2WO6 showed a lower charge-transfer resistance, higher photocurrent and enhanced photoelectric properties. The photocurrent of the 15% BiOBr/Bi2WO6 composite was 17.2 and 2.39 times higher than that of pure Bi2WO6 and BiOBr, respectively. Meanwhile, this composite showed the highest degradation rate for methylene blue (MB), which was 1.7 and 2.4 times that of pure Bi2WO6 and BiOBr, respectively. The enhanced photoelectric and photocatalytic degradation performances were ascribed to the introduction of BiOBr nanodots and the formation of p-n heterojunctions, which could greatly accelerate the separation of photogenerated charge carriers. In addition, the roles of the radical species were investigated, and center dot O-2(-) and h(+) are thought to dominate the photocatalytic process. Based on the experimental results, a possible photocatalytic mechanism was proposed.