BiOBr nanoflakes-decorated BiPO4 (BiOBr/BiPO4) composite photocatalysts were prepared by a simple hydrothermal method. The BiOBr nanoflakes were tightly dispersed on the surface of the BiPO4 and formed p-n heterojunctions between BiOBr and BiPO4, as evidenced by characterization of the structure and composition. The p-n heterojunctions BiOBr/BiPO4 composites could greatly improve photocatalytic activity, and the 60 wt% BiOBr/BiPO4 composite showed the highest degrade rate for methylene blue (MB), which was eight times and two times than that of pure BiPO4 and BiOBr, meanwhile, the BiOBr/BiPO4 composite also exhibited superior activities for phenol degradation under visible light. The enhanced photocatalytic performance was attributed to the enhancement of visible-light absorption efficiency as well as the formation of p-n heterojunctions in BiOBr/BiPO4, which could greatly accelerate the separation efficiency of photogenerated charge carriers. In addition, the roles of the radical species were investigated, and the O-2(-) and h(+) were thought to dominate the photocatalytic process. Based on the experimental and theoretical results, the possible photocatalytic mechanism was proposed. (C) 2015 Elsevier B.V. All rights reserved.