The Preparation And Properties Of Plasmonic TiO₂ Photocatalyst

Now the world faces the chanllenges of energy shortage, environment pollution with the accelerating process of global industrialization which has pose a threat to the human health and living environment. How quickly and effectively to achieve the pollution problems of sustainable development has become a primary consideration problem. Semiconductor photocatalysts can convert the solar energy to hydrogen energy. Especially, 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. But with increasing depth study, there are some obstacles to its effective utilization, including the relatively inefficient utilization of solar energy and low quantum yields. It is very necessary to find a new and more efficient visible-light photocatalyst to meet the requirements of future environmental and energy technologies driven by solar energy.This study put forward plasmonic photocatalyst based on the noble metal nanoparticles'surface plasmon resonance(SPR). Then by changing the morphology of photocatalysts, such as hollow spheres, nanotubes/belts, films, the materials'photodegradation can be enhanced and easy to separate. This thesis covers the following aspects:(1) Synthesis and properties of plasma-based films.Stable and spherical colloidal Ag nanoparticles were prepared by chemical reduction method. Results show that the pure and spherical Ag NPs were formed at 90℃by using 40min, and had the highest SPR peak. The final colloidal Ag NPs had narrow size distribution in 20-30nm, and remained stable for one month at room temperature. The Ag/SiO₂/TiO₂ film samples with different layers and types were synthesized by sol-gel method. The degradation of MB photocatalytic degradation rate and degradation kinetics results of samples show that the TiO₂ photocatalyt with one layer of Ag and one layer of protective dielectric SiO₂ shows best degradation. This mainly caused from the Ag surface plasmon resonance effect which can enhance the absorption of ultraviolet lights on TiO₂ thin films. And SiO₂ dielectric layer prevent the oxidation after the direct contact with Ag and TiO₂. Finally, the sample's degradation rate of MB after UV irradiation 2h reaches to 65%.(2)Ag@AgI Supported TiO₂ Acid Corrosion Nanobelts Plasma Photocatalyst: Synthesis and Visible Light Photocatalytic PerformanceA Ag@AgI supported TiO₂ acid corrosion nanobelts plasma photocatalyst was prepared by deposition-precipitation method and photo reduction method. The products were characterized by XRD, SEM and UV-Vis spectroscopy. The photocatalytic activity was evaluated using methyl orange (MO) degradation under visible light irradiation as a probe reaction. The results indicate that the corrosion nanobelts are benificial for AgI deposition. The surface plasmon resonance of Ag can enhance the visible light absorption of photocatalyst. The TiO₂ acid corrosion nanobelts supported with Ag@AgI photocatalyst shows the highest photodegradation of MO under visible light.(3) The properties of Ag plasmonic enhanced CdS-TiO₂ nanotubes photocatalyst.Firstly, TiO₂NTs were prepared by hydrothermal method. And then by hydrothermal method and chemical reduction, Ag-CdS/TiO₂ composite photocatalyst was prepared. Its photoatalytic properties under visible light through nitrobenzene and simulated sunlight through aquaculture wastewater were investigated through visible light and simulated sunlight nitrobenzene aquaculture wastewater degradation. The results show that photocatalytic activity of composite photocatalyst was significantly increased than pure TiO₂ photocatalyt. The light electrons and holes can be effectively separated, which is caused by the complex of narrow gap semiconductor CdS and the deposition of Ag.(4) Preparation and properties of Ag@SiO₂@TiO₂.At first, Ag@C core-shell microspheres templates were synthesized by hydrothemal method. By morphology analysis, the synthesis conditions of Ag@C template were determined. Ag@SiO₂@TiO₂ hollow spheres were prepared by surface depsition and template oxidation removal stage. Sample's calcination temperature, crystalline phase, morphology and ability to the spectral response were characterized by TG/DTA, XRD, TEM, SEM and UV-Vis spectroscopy analysis. The photocatalytic degradation of MB solution under UV light was found: AgNO3 adding amount of 1.0ml, calcination temperature of 500℃Ag@SiO₂@TiO₂ samples show the highest photocatalytic activity which is 84% in120min.