Study On The Synthesis And Photocatalytic Properties Of The Solar Energy Photocatalysts

In recent years, photocatalysis has been a one-up field in photochemistry, and has widely applied foreground in disposing organic waste water. Now, it is the major research direction how to synthesize the sunlight-driven photocatalysts and further apply the photocatalysts to the wastewater treatment. The current reseach is focused on the following two aspects: one is the exploring synthesis methods of photocatalysts with high specific surface areas, and promoting the adsorption properties of the synthesized phtocatalysts, and consequently promoting photocatalytic degradation activities of the photocatalysts on the pollutants; and the other is how to selecte the sunlight-driven photocatalysts and make it applicable to use photocatalytic oxidation technique in real waste water treatment.The thesis can be divided into four parts: the first chapter is the research grounds of photocatalysis; The second is the study on the synthesis of CdS hollow spheres and their photocatalytic properties; The third is the study of effects of different synthesis methods on the photocatlytic properties of SrCoO_x; And the forth is the study of the preparation of compound metal oxidation containing bismuth and their photocatalytic properties.The following is the concrete contents of every chapter:The purpose of the first chapter is to summarize the fundamental principles, characterizations and applied ranges of photocatalysis, further to investigate the research actuality of TiO₂ as photocatalyst and its defects,and the advantages of sunlight-driven photocatalysts as potential photocatalysts. Based on the above overviews, I put forth my tentative plans and some ideas to apply photocatalytic oxidation techniques to real application.In the second chapter, CdS hollow spheres with the diameter of 80-120 nm were successfully synthesized in the system of oil in water emulsion and characterized by the XRD, SEM, TEM and UV-Vis technologies. The formation mechanism of CdS hollow spheres was also discussed. The photocatalytic activity of CdS hollow spheres has been tested on the decomposable substrate methylene blue under sunlight illumination. Test results showed that methylene blue was completely decomposed within just 60 min.In the third chapter, SrCoO_x photocatalysts were successfully synthesized by using the different synthesis methods of citric acid complex method and the solid-phase method. SrCoO_x powders have hexagonal crystal system structure through XRD analysis. Through UV-Vis reflectance spectra, it can be seen that the synthesized products have good photo absorption properties. Using sun as light source, the decomposition experiments of water soluble dye safranine T were carried out in the suspension liquid with SrCoO_x to investigate the photocatalytic properties of SrCoO_x. The results showed showed that SrCoO_x showed stronger photocatalytic activity by using citric acid complex method than that of SrCoO_x by using solid-phase method, and the dye decolorization ratio is up to 95.2% through 4.5 h under sunlight irradiation, which demonstrated that SrCoO_x phtocatalysts have good photocatalytic property.The forth chapter was divided into three parts:1. Bi₃₈ZnO₅₈ was successfully synthesized by means of solid state reaction method. The photo-absorption property was determined by UV-Vis diffuse reflectance spectrum, from which it could be seen that Bi₃₈ZnO₅₈ owned much strong photo-absorption property both in the ultraviolet and visible light regions. The photocatalytic activity of Bi₃₈ZnO₅₈ was tested on methylene blue solution under sunlight illumination. The test results showed that methylene blue was nearly completely degraded after 4 h, which confirmed the high photocatalytic activity of the photocatalyst. Moreover, the crystal structure of Bi₃₈ZnO₅₈ was still unvaried and its photocatalytic efficiency was still above 98% even after being reused for five times, which demonstrated the high stability of the photocatalyst. 2. In this chapter, BiVO₄ micro-rods with brick shape were successfully synthesized in the system of polyglycol/cyclohexane/water emulsion and under ultrasonic condition, and characterized by the XRD,SEM,TEM and UV-Vis technologies. BiVO₄ micro-rods with brick shape, which were composed of nano-particles, have strong photo-absorption property both in the UV region and the visible light region. The formation mechanism of BiVO₄ micro-rods was also discussed tentatively. The photocatalytic activity of BiVO₄ micro-rods had been tested on the decomposable substrate methylene blue under sunlight illumination. Test results revealed that methylene blue was completely decomposed within just 60 min, which made the catalyst have greatly potential applications.3. In this chapter, Bi₂₀MoO₃₃ photocatalysts were successfully synthesized by the solid-state reaction method, and characterized by the XRD,SEM and UV-Vis technologies. Test results showed that Bi₂₀MoO₃₃ photocatalyst has strong photo-absorption property both in the UV region and the visible light region. The photocatalytic activity of Bi₂₀MoO₃₃ photocatalyst had been tested on the decomposable substrate methylene blue under sunlight illumination. Test results revealed that the degradation ratio of methylene blue was up to 84% through 8 h under sunlight irradiation, which made photocatalyst have greatly potential applications.