The Study Of Heterostructure TiO₂ Photocatalyst

The negative effects of highly developed industry was not be predicted and prevented adequately, therefore, it leads to a global environmental crisis, which seriously affects people's health, how to effectively solve this problem has become the direction of the work of many scholars. The technology of organic wastewater semiconductor catalytic oxidation is a cheap and environment friendly technology, in many semiconductor oxides, nanometer, TiO₂ has a good chemical stability, low cost, corrosion-resistant, non-toxic and unique optical, electrical properties, so it has expressed good application prospect on degrading organic contaminants in wastage. However, TiO₂ is a wide band gap semiconductor, so its quantum yield is low, and it is difficult to separate, recycle and reuse. Therefore, in this paper, the photocatalytic activity of TiO₂ under visible light is increased by compounding with different types of semiconductor and metal, and the magnetic carriers are used to make it easy to separate, recycle and reuse, the following aspects were mainly studied.1. The process parameters of TiO₂ photocatalysts prepared by sovolthermal method were studied, and its photocatalytic activity was compared with the TiO₂ prepared by Sol-Gel method. The results show that when the surface active agent was added and the reaction temperature was 180℃, the surface area of the TiO₂ prepared by sovolthermal method was the largest, and its grain size is less than the TiO₂ prepared by Sol-Gel method, under visible light irradiation, the degradation rate of nitrobenzene is as high as 75% after 4h, it was higher than the TiO₂ prepared by Sol-Gel method.2. A novel composite heterojunction photocatalysts Sr(Zr1-xYx)O3/ TiO₂/ CdS was prepared by sol-gel combustion method. Its photoatalytic properties under visible light were investigated through degradation of methyl orange. XRD,SEM,Uv-Vis and PL techniques were used to characterize the structure and optical properties of the sample. The results showed that the photocatalytic activity of prepared composite photocatalysts under visible light is 2.85 times of that of pure TiO₂ photocatalysts under visible light is 2.85 times of that of pure TiO₂. The results indicated that the narrow bandgap energy CdS made the composite heterojunction photocatalyst a visible light response type photocatalyst, and the high photocatalytic photocatalytic activity of composite photocatalyst came from the effective separation of photogenerated electron and hole.3. The composite photocatalysts Ag/SiO2/TiO₂ were prepared by sovolthermal methord, the effections on the photocatalytic activity of surface plasmon resonance, SiO2 layer and the composite volume of Ag/SiO2 were investigated through degradation of methyl orang under visible light. The results showed that the Schottky junction formed by TiO₂ and Ag promotes the electrons and holes separated, and the strong absorption in the UV region caused by the surface plasmon resonance of AgNPS extended the response range of TiO₂, the SiO2 layer acted successfully as a barrier on the Ag NPs. The photocatalytic experimental results showed that the photocatalytic activity of the sample Ag/SiO2/TiO₂(the composite quantity of Ag/SiO2 was 15%)was the highest, the degradation rate of methyl orang was 72.1% after 5h. This showed that that Ag NPs potentially retard furthermore the recombination of electron-hole pairs. In conjunction with the surface plasmon resonance it gives rise to the observed enhancement in photocatalytic activity.4. The magnetic nanocomposite NiFe2O4/SiO2/TiO₂ was prepared by sovolthermal method, the photocatalytic degradation and oxidation of aqueous phenol solution has been studied under visible light. The results showed that the electric field of heterojunction promotes the effective separation of electrons and holes.The photocatalyst showed properties of absorptive wavelength red-shift by UV-vis analysis, its band gap was 2.3eV. The VSM analysis showed that the photocatalyst had good magnetic properties. This showed that the SiO2 layer prevented successfully electron and hole to transfer to the NiFe2O4, and the magnetic nuclei of Fe3+, Ni2+ enhanced photocatalytic activity of the conductor.