BiOI/BiOBr heterostructures, synthesized by a simple chemical etching method using acetic acid and KI as etching agents to react with BiOBr particles, were characterized by X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and Brunauer-Emmett-Teller (BET) surface area. The as-prepared samples exhibited more efficient photocatalytic activities than pure BiOI and BiOBr for the degradation of methyl orange (MO) under visible light irradiation (lambda > 420 nm), which could be attributed to the efficient separation of electron-hole pairs caused by the formation of BiOI-BiOBr heterojunction. Terephthalic acid photoluminescence (TA-PL) probing test and radical scavenger's experiments demonstrated that h(+), center dot O-2(-) and H2O2 were the dominant reactive species while (sic)OH could be negligible. A possible transfer process of photogenerated carriers was proposed based on the band structures of BiOI and BiOBr (c) 2012 Elsevier B.V. All rights reserved.