A series of nitrogen and nickel-chlorine co-modified TiO2 photocatalysts (TiO2-N-x%Ni) with visible-light response have been synthesized by a sol-gel method. The results of photocatalytic degradation of 4-chlorophenol (4-CP) suggest that TiO2-N-x%Ni photocatalyst shows a higher activity than both pure TiO2 and nitrogen doped TiO2 (TiO2-N) under visible-light irradiation. The structure and properties of the photocatalysts have been investigated by XRD, XPS, UV-vis diffuse reflectance spectra (DRS), and photoluminescence (PL) spectra. It was found that unique chemical species, such as N-O-x and O-Ni-Cl, existed on the surface of TiO2-N-x%Ni. The energy levels of N-O-x and O-Ni-Cl surface states locate above the valence band and below the conduction band of TiO2, respectively. This could lead to strong visible-light absorption and an enhanced charge carrier separation compared with both pure and TiO2-N. Our results offer a paradigm for preparation of photocatalyst with a high visible-light activity by simultaneously doping TiO2 with two or more different elements. (C) 2012 Elsevier B.V. All rights reserved.