| TiO2-based semiconductor photocatalysis technology has been shown to be potentially advantageous for environmental remediation as it may lead to complete mineralization of pollutants at ambient conditions with the use of ultraviolet light as the energy source. However, TiO2 is actived only by irradiating with ultraviolet light due to its large band gap of 3.2 eV, corresponding to wavelengths shorter than 388 nm.This means that TiO2 could make use of only a small fraction(～5%) of the sun's energy compared to the visible region(45%). So it is important to look for a method that can shift the optical response of TiO2 and make it be able to photocatalyze oxidation of organic in low energy light such as visible light.Referring to the Previous works, inrtoducing doping ions in TiO2 known as an effective method by which its photocatalystic ability can be improved. Therefore in the thesis, the TiO2 doped with various ions have been synthesized by the sol-gel route. And their performance in the photocatalystic activity and photooxidation rate has been also rated.(1)N,Dy-codoped TiO2,Dy-doped sample, N-doped sample, and pure TiO2 photocatalyst was synthesized by the sol-gel route in this paper. Preparation of pure TiO2, N doped TiO2, Dy doped TiO2, N,Dy co-doped TiO2 calcined at 450℃, showed a good crystallinity, both anatase. N doped TiO2, Dy doped TiO2,N,Dy co-doped TiO2, is smaller than that of pure TiO2, particle size, N,Dy co-doped TiO2, particle size of the smallest, indicating that N,Dy doping elements inhibit grain growth, and N,Dy elements can play a synergistic effect, a common grain growth inhibiting titanium dioxide. With the heat treatment temperature, the pure TiO2 at 600℃has become the main phase of rutile, but after the TiO2 doped at 600℃still the main phase of its anatase phase, indicating that N,Dy doping element can inhibit the transformation of titanium dioxide crystal. The results showed that the absorbance spectra of N, Dy-codoped TiO2 exhibited a significant red shift to the visible region and its photocatalystic ability was improved. When the Ti, N and Dy mole ratio of 1:2:0.5%, the N,Dy-codoped TiO2 has the best photocatalytic activity.(2)N,Gd codoped TiO2,Gd-doped sample, N-doped sample, and pure TiO2 photocatalyst was synthesized by the sol-gel route in this paper. The samples prepared at 450℃calcined, are nano-particle size. After doped, the nano-particle size of titanium dioxide are smaller than the particle size of pure titanium dioxide, codoped titanium dioxide has he smallest particle size, indicating that doping elements played a role in inhibiting grain growth, nitrogen gadolinium two kinds of elements played a good synergy, to jointly suppress grain growth of titanium dioxide. With the heat treatment temperature, the sample crystal transition occurred gradually. At 600℃, the pure titanium dioxide has been the main phase of its original anatase phase into rutile phase; N,Gd codoped titanium dioxide rutile has also emerged, but still the main phase of anatase, This shows that the nitrogen doped gadolinium elements played a role in inhibiting crystal phase transition..The results showed the photocatalystic ability of N,Gd-codoped TiO2 was improved and the improvement of the photocatalytic activity was ascribed to the synergistic effects of the N and Gd co-doping. When the Ti, N and Gd mole ratio of 1:2:0.5%, the N,Gd-codoped TiO2 has the best photocatalytic activity.(3) the photocatalystic ability of N,Gd-codoped TiO2 was better than he photocatalystic ability of N,Dy-codoped TiO2, it may be due to Gd3+... |
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