Synthesis and characterization of visible-light-active mesoporous titania by doping Ni and N

Ultrafine TiO₂ nanoparticles with a narrow size distribution were designed for extending the light absorption wavelength from ultraviolet to visible light with the increased photocatalytic activity. The mesoporous spherical TiO₂ nanoparticles and the Ni doped TiO₂ nanoparticles were prepared by sol–gel method, with the Ni molar fraction ranged from 0.5, 1, 2, 3, 4 to 5%. Samples were calcined at 550 °C to form crystallized TiO₂ and eliminate organic impurities. The Ni and N co-doped TiO₂ nanocrystals were prepared by heating Ni doped TiO₂ powders in NH₃ flow at 650 °C. All the doped titania nanocrystals are well crystallized anatase with a tetragonal structure. 0.5% Ni–TiO₂ exhibited optimum photocatalytic activity for MB degradation under UV-light irradiation, which was about twice compared to that of the blank TiO₂. The visible light photocatalytic activity of 5% Ni/N-TiO₂ was remarkably raised up to 4 times by contrast with the blank TiO₂ while the photocatalytic activity of N-TiO₂ only increased to 2 times compared to that of the blank TiO₂.