Modification Of Tio <sub> 2 </ Sub> Photocatalyst

Electron-hole pairs will be generated upon excitation by light with energy equal to or greater than the band gap of TiO2. Since the strong oxidative power of the photogenerated hoes makes it possible to oxidize most of pol lutants and to transform some of the toxic inorganic pollutants into harmless forms as well. Photocatalysis of TiO2 is significant for environmental remediation.But TiO2 can photocatalyze oxidation of organic only in the irradiation of high light ,such as Ultraviolet(UV),due to its high band gap(Eg = 3.2eV).So it is highly important to look for a new kind of modified catalyst and make it be able to photocatalyze oxidation of organic in low energy light such as visible light.After extensive and intensive analysis of the mechanism of TiO2 photocatalyst and the electronic structure of TiO2, we planed to dope TiO2 with CdS, making its photo response wavelength expand to longer wave ,and Fe3+, inhibiting the recombination of photo induceelectron and hole. Then we successfully prepared about twelve kind of modified photocatalysts. We have studied the preparation of TiO2 doped systems in detail to find the factors that affect its photocatalysis activities. By XRD analysis, it was proved that CdS had been doped into the crystal structure of TiO2 and thus formed new substance CdTiO3 and Fe3+ was doped into TiO2 as non-crystalline. Then by UV-Vis analysis, it was proved that the doping of CdS and Fe3+ made the response light energy decrease to visible light, and when Cd/Ti is about 2%(molar ratio), the expansion of absorbed light strength in visible light area is most obvious in TiO2-CdS doped system, Fe3+/Ti about 1% in TiO2-Fe3+ doped system.At last, the results of photocatalyzing oxidation of methyl orange by doped systems showed that doping TiO2 with CdS can enhance the photocatalytic activity of catalyst ,and when CdS/TiO2 is about 0.5%(molar ratio),the oxidation rate of methyl orange in 2.5 hours of the catalyst is twice larger than that of TiO2. At the same time, by the study of the dynamics of the oxidation of methyl orange ,it showed that the reaction is quite in agreement with the Y = A + B1*X + B2*X2 dynamic model. But doping TiO2 with Fe3+ can decrease the photocatalytic activity of catalyst tempestuously.