Mesoporous anatase phase TiO2 was assembled on reduced graphene oxide (rGO) using a template-free one-step hydrothermal process. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron, spectroscopy (XPS), Raman spectroscopy, and Brunauer-Emmett-Teller (BET) surface area. Morphology of TiO2 was related to the content of graphene oxide. TiO2/rGO nanocomposites exhibited excellent photocatalytic activity for the photo-degradation of methyl orange. The degradation rate was 4.5 times greater than that of pure TiO2 nanoparticles. This difference was attributed to the thin two-dimensional graphene sheet. The graphene sheet had a large surface area, high adsorption capacity, and acted as a good electron acceptor for the transfer of photo-generated electrons from the conduction band of TiO2. The enhanced surface adsorption characteristics and excellent charge transport separation were independent properties of the photocatalytic degradation process. (C) 2014 Elsevier Ltd. All rights reserved.