In the present work, graphene-TiO2 (GR-TiO2) photocatalyst with various weight ratios of graphene was synthesized using peroxo titanic acid solution (PTA) as a precursor for TiO2. Graphene oxide prepared by Hummer's method was converted to graphene under ultraviolet (UV) irradiation in ethanol-water solvent for 48 h. The as-prepared GR-TiO2 composites were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectrophotometry, and transmission electron microscopy (TEM). The automated potentiostat was applied to measure the photocurrent generations of prepared catalysts. The photocatalytic activities of GR-TiO2 (PTA) catalysts were determined by measuring the percentage methylene blue (MB) degradation. The results showed that TiO2 nanoparticles were successfully loaded onto graphene sheet and the surface area of catalysts increased with increasing weight ratio of graphene. In addition, GR-TiO2 (PTA, 1:50) exhibited the highest photocatalytic activity among the catalysts under UV and visible light irradiation. The adsorption edge of GR-TiO2 was shifted to a longer wavelength of 400 nm in comparison with that of pure TiO2 (PTA). The increase in the photocatalytic performance of GR-TiO2 (PTA) catalyst may be attributed to the increase in surface area, the extension of light absorption in the visible light region, and prevention of charge recombination. (C) 2013 Elsevier Ltd. All rights reserved.