▎ 摘　　要

Nitrogen doped TiO2 nanoparticles decorated on graphene sheets are successfully synthesized by a low-temperature hydrothermal method. The resulting GR-N/TiO2 composites are characterized by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-Ray photoelectron spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The optical properties are studied using UV-visible diffuse reflectance spectroscopy (DRS), which confirms that the spectral responses of the composite catalysts are extended to the visible-light region and show a significant reduction in band gap energy from 3.18 to 2.64 eV. Photoluminescence emission spectra verify that GR-N/TiO2 composites possess better charge separation capability than pure TiO2. The photocatalytic activity is tested by degradation of methyl orange (MO) dye under visible light irradiation. The results demonstrate that GR-N/TiO2 composites can effectively photodegrade MO, showing an impressive photocatalytic enhancement over pure TiO2. The dramatically enhanced activity of composite photocatalysts can be attributed to great adsorption of dyes, enhanced visible light absorption and efficient charge separation and transfer processes. This work may provide new insights into the design of novel composite photocatalysts system with efficient visible light activity. (C) 2012 Elsevier B.V. All rights reserved.