Photocatalytic activity of Ni 8 wt%-doped TiO2 photocatalyst synthesized by mechanical alloying under visible light

Ni 8 wt%-doped titanium dioxide (TiO2) was synthesized by mechanical alloying. The photocatalytic activity of Ni 8 wt%-doped TiO2 powder was evaluated by measuring the visible light absorption ability by ultraviolet visible diffuse reflectance spectroscopy (UV/Vis-DRS) and photoluminescence (PL) spectroscopy. Ni 8 wt%-doped TiO2 powders had only a rutile phase and spherical particles with an average grain size of less than 10 nm. The UV/Vis-DRS analysis showed that the UV absorption for the Ni 8 wt%-doped TiO2 powder moved to a longer wavelength and the photoreactivity was rapidly enhanced. And PL results revealed that the new absorption was believed to be induced by localization of the trapping level near the valance band or conduction band. Moreover, Ni 8 wt%-doped TiO2 had a high reaction activity for decomposition of 4-chlorophenol in aqueous solution under UV and visible light. To obtain the electronic structure of Ni-doped TiO2, we have performed ab initio pseudopotential plane wave methods based on the density functional theory. The band gap of Ni-doped TiO2 narrowed more than pure TiO2. These results agree with the experimentally observed phenomenon.