A one-step hydrothermal method was adopted to synthesize the Ag2O/TiO2 nanoheterojunction. Its photocatalytic activity was evaluated by degrading methylene blue (MB) aqueous solution under UV and visible light. The MB degradation results showed that the Ag2O/TiO2 nanoheterojunction enhances the photocatalytic activity under UV irradiation rather than visible light. X-ray photoelectron spectroscopy (XPS) was performed to detect the electronic structure at the interface of Ag2O and TiO2. The XPS results confirmed that the electronic band structure of the nanoheterojunction was determined by the interface states between the Ag2O and TiO2 interface. Thus, the photocatalytic enhancement mechanism can be ascribed to the creation of an additional potential barrier in the conduction band between Ag2O and TiO2, which facilitates the transport of holes from TiO2 to Ag2O but inhibits the flow of electrons in the reverse direction unless sufficient potential energy is provided to overcome the additional barrier. Our results have provided a new insight on the role of interface states between the p-n nanojunction in the photocatalytic activity. (C) 2017 Elsevier Inc. All rights reserved.