A composite semiconductor AgBr/Ag5P3O10 heterojunction has been synthesized by a simple one-step ion-exchange process in Br ionic liquids. All the as-obtained AgBr/Ag5P3O105 heterojunctions were characterized by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), Brunauer-Emmett-Teller (BET), UV-vis absorption spectroscopy (UV-vis), photoluminescence (PL), and surface photovoltage (SPS) techniques. The as-prepared AgBr/Ag5P3O10 heterojunctions intensively absorb in the visible light region. The effects of different conditions on the photocatalytic properties were investigated systematically. The AgBr/Ag5P3O10 heterojunctions exhibited an enhanced photocatalytic activity than the individual Ag5P3O10 did in the degradation of methylene blue (MB) under visible-light irradiation. Much more OH radicals were found in the AgBr/Ag5P3O10 system in comparison with those in Ag5P3O10 alone by analyzing the formed .OH radicals under visible light radiation. The SPS measurement shows that the SPS amplitude of AgBr/Ag5P3O10 heterojunctions was higher than that of Ag3P3O10, which indicates the higher charge separation efficiency of AgBr/Ag5P3O10 heterojunctions. Based on the above experimental results, the kinetic data and the photocatalytic mechanism of the AgBr/Ag5P3O10 heterojunctions were discussed in detail. (C) 2012 Elsevier B.V. All rights reserved.