Synthesis and characterization of BiOI/BiOBr heterostructure films with enhanced visible light photocatalytic activity

•BiOI/BiOBr heterostructure films were synthesized by a solvothermal method.•Effect of BiOI content on heterojunction structures of BiOI/BiOBr film was studied.•BiOI/BiOBr heterostructure films exhibit enhanced photocatalytic activities.•The optimal BiOI content for the best photocatalytic activity was identified. BiOI/BiOBr films were successfully prepared via a facile solvothermal method. The as-prepared films were characterized by XRD, SEM, TEM, N2-sorption, PL and UV–vis DRS spectra. The photocatalytic activity of the BiOI/BiOBr films was evaluated by the decomposition of methyl orange (MO) under visible light irradiation. Compared with pure BiOBr film, BiOI/BiOBr films exhibited significantly enhanced photocatalytic activity. The highest photocatalytic activity was achieved by 40%BiOI/BiOBr film. The enhanced photocatalytic performance was attributed to high specific surface area, appropriate energy band gap and low recombination rate of the photogenerated electron–hole pairs at the hetero-interfaces and in the semiconductors.