Preparation, Characterization And Photocatalytic Activity Of Tio 2 Particles Modified With V

The utilization of solar energy, a clear energy, control and treatment of environmental pollution are important problem that should be faced and resolved in 21th century. So the research and development on cheap photocatalysts with high performance, which can utilize solar energy directly and environmental friendly, have enormous social and economic benefit.In order to enhance the photocatalytic activity of TiO2 catalysts, highly active TiO2/V–TiO2 composite photocatalysts with an n-n heterojunction semiconductor structure has been prepared by mixing TiO2 sol with sol–gel derived V–TiO2 powders that have adsorbed ammonium oleate in advance, followed by drying and calcination. These composite photocatalysts were characterized by XRD, TEM, BET, XPS, UV–vis and PL spectroscopy. The photocatalytic activities of TiO2-based nanoparticles were evaluated by the photocatalytic rate of methyl orange oxidation under UV light irradiation. The influence of doping concentration of metal ions, doping modes and amount of dopants on the photocatalytic activities were investigated. The results were showed as follows:(1) The photocatalytic activities of modified titania with rare V ion by even doping mode showed little improvement. The reason is when the metal ions were even doped, they would increase of the electron-hole pair separation efficiency, but in the same time they would become recombination centers of the electron-hole pairs.(2) The modified titania with V metal ion by uneven doping mode displayed better photocatalytic activities, and the apparent rate constant(k) was 5.9 times as high as that of pure TiO2.(3) XRD patterns of the TiO2-based nanoparticles can be indexed to the anatase phase only, and the grain size of TiO2/V–TiO2 composites is slightly larger than that of undoped titania. TEM images reveal that the prepared samples consisted of aggregates of primary particles of 20–35 nm in diameter, which is in general agreement with the XRD determination.(4) XPS spectra shows the O1s peak can be fitted into two Gaussian peaks at about 529.6 and 531.4 eV, which arise from lattice oxygen (O2–) of titania and surface hydroxyl groups on titania surface, respectively . In addition, there is no signal of vanadium for vanadium-containing TiO2, due to the low vanadium content.(5) UV-vis DRS results indicated that TiO2-based photocatalysts showed enhanced absorptions in the range from 400 to 600 nm with increasing vanadium content, accompanied with the changes on color from white to grey brown.(6) Photoluminescence spectra exhibit seven main emission peaks at about 399, 413, 421, 453, 469, 483 and 493 nm with excitation at 320 nm. The great decrease in emission intensity of V–TiO2 compared with undoped TiO2 may be due to the impurity levels introduced by dopant that enhanced non-radiative recombination of the excited electrons.