Synthesis And Visible-light Photocatalytic Performance Of Silver Iodide Composite Materials

With rapid developments within society and industry, energy crises and environment pollution are becoming evenmore serious. To resolve these problems, semiconductor catalysts have received attention because of their applications in solar energy conversion and photo-oxidation of organic pollutants. Over recent decades TiO2 has been the subject of extensive investigation because of its high efficiency, low cost, non-toxicity and high stability. However, due to its wide band gap, only the ultra-violet light(4% of the solar light spectrum) can be absorbed, which greatly limits their visible-light photocatalytic activity and practical application. Given the conditions above, researches on high-efficiency visible-light-driven heterogeneous photocatalysts have become hot issues in the photocatalysis field. However, AgX-based photocatalysts have proved an effective way to broaden the photoabsorption range and facilitate the separation of the photoinduced carriers. The general way is loading AgI particles as visible light active components on different substrates to form composites, in order to make the wavelength with a red shift. Therefore, design and synthesis of Ag I composite with novel structures and properties are of special significance.The main contents of this thesis are listed as below:(1) The Ag/AgI heterojunction was prepared by a facile, one-step and low-temperature hydrothermal synthesis method with P, I2 and Ag2 O. The samples were carefully characterised by X-ray diffraction, X-ray photoelectronic spectra, scanning electronmicroscopy, transmission electron micrographs and ultraviolet–visible-light techniques. The results show that the optimum reaction condition of Ag/AgI is 4 h at 120 oC. What’s more, Ag nanoparticles were uniformly distributed on the surface of AgI and the heterostructure was formed. Under visible light, 97.8% of RhB has been degraded. The possible mechanism of degradation was discussed.(2) ZnO followers were synthesized by hydrothermal synthesis. The AgI/ZnO heterojunction of different theoretical molar ratios of Ag/Zn was successfully synthesized by in situ deposition method. The photocatalytic efficiency of AgI/ZnO was evaluated by the degradation of rhodamine B under visible light irradiation. The influence of various operational parameters such as the effect of loading amount, catalyst dosage and initial RhB concentration on the photodegradation was investigated in detail and the results were discussed. The results indicated that the optimum reaction conditions are AgI content 10%, AgI/ZnO concentration 0.3 g/L and RhB initial concentration 0.01 mM. In this thesis, the enhanced photocatalytic activity was investigated on these factors. At last, the possible mechanism of degradation, cycling stability, and applications of dye degradation under natural sunlight were discussed.(3) 3D dandelion-like TiO2 microspheres were prepared by a solvothermal method. The AgI/TiO2 composite of different theoretical molar ratios of Ag/Zn was successfully synthesized by in situ deposition method. The photocatalytic efficiency of AgI/TiO2 was evaluated by the degradation of reactive brilliant red X-3B under visible light irradiation. The influence of various operational parameters such as the effect of loading amount, dyestuff type and light source on the photodegradation was investigated in detail and the results were discussed. The results indicated that the optimum reaction conditions are AgI content 15%, AgI/TiO2 concentration 1.6 g/L and X-3B initial concentration 80 mg/L. In this thesis, the enhanced photocatalytic activity was investigated on these factors. At last, the possible mechanism of degradation, cycling stability, and applications of dye degradation under natural sunlight were discussed.