An enhanced visible-light photocatalytic activity of TiO2 by nitrogen and nickel–chlorine modification

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–Ox and O–Ni–Cl, existed on the surface of TiO2-N–x%Ni. The energy levels of N–Ox 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.

The co-modified N and Ni–Cl in the catalyst exist as surface species, which result in an enhanced visible-light response and an efficient separation of photoinduced charges in the TiO2-N–x%Ni samples.Figure optionsDownload as PowerPoint slideHighlights
► The doped Ni and Cl in the catalyst exist as O–Ni–Cl surface species.
► The doped N in the catalyst exist as N–Ox surface species.
► The surface state energy level will result in an enhanced visible light absorbance.
► The band structure and photocatalytic mechanism of the samples are discussed.