Preparation Of Zinc-base Oxide And Its Composites And The Research Of Their Photocatalytic Performance

Photocatalytic technology is a kind of green environmental protection technology. The reaction condition is mild, and the scope of application is widespread, especially in the removal of organic pollutants and produce clean energy. In recent years, its research has caused wide attention. However, the performance of the photocatalyst become the key issues of the development of photocatalytic technology. So the semiconductor photocatalyst with excellent properties draw the peoples’ attention. Semiconductor photocatalyst has many advantages such as high efficiency, low energy consumption, mild reaction condition, and no secondary pollution. When the semiconductor photocatalyst excited by the sunlight, it can effectively produce electronic and holes, and the organic pollutants can be converted to small molecules H2 O and CO2, so far a to the organic pollutants difficult to degrade such as methylene blue（MB） and rhodamine B（RhB）. Semiconductor photocatalyst can also be used to photocatalytic reduce water to hydrogen and reduce CO2 to energy. Nevertheless, the light absorption range of semiconductor photocatalyst, photocatalytic efficiency and photochemical stability are all not satisfactory, so the development of novel, stable and efficient semiconductor photocatalyst is still a huge challenges to the development of photocatalytic technology. To solve above problems, this paper studies the preparation of semiconductor of ZnO flowers, Zn₂GeO₄ nanorods, Zn₂GeO₄/GO and Zn₂GeO₄/g-C₃N₄ nanocomposites. The main contents are as follows:（1） The ZnO flowers semiconductor photocatalysts has been prepared through the solvent thermal method without any surfactant or alkaline reagents. We chose glycerol and isopropyl alcohol as the solvents. The method is simple, raw materials is clean andinexpensive. Morever, the method for the preparation of the flwer-like ZnO can be used to other oxide. Then we used X-ray diffraction（XRD）, scanning electron microscope（SEM） to analysis the phase and morphology of the product, use infrared（FT-IR）, X-ray diffraction（XRD） and thermogravimetric analysis（TGA） to characterize the precursor of the product and infer its forming mechanism. Finally, we test its specific surface area through the nitrogen adsorption-stripping analysis（BET） and measure the spectral absorption range by ultraviolet spectrophotometer（UV-Vis）. The photocatalytic degradation of rhodamine B efficiency above99% under ultraviolet light（UV-light）.（2） The Zn₂GeO₄ nanorod has been synthesized through the two-step solvent thermal method. We prepared the precursor by solvent thermal method first, then added germanium dioxide to the system, and then hydrothermal reaction again. The phase and morphology of the product were characterized by XRD, SEM and TEM. The results indicate that the morphology and size of Zn₂GeO₄ nanorods is uniform, and it can degrade RhB under UV-light, and the degradation rate reaches 70.36%.（3） The Zn₂GeO₄ nanocrystalline are prepared via solvothermal method and loaded on the graphene oxide（GO）. The Zn₂GeO₄/GO nanocomposite has been synthesized through a simple two-steps reaction. The structure, topography and the optical property of the photocatalys were characterized by XRD, TEM and UV-Vis. RhB was used as the degradation agent to evaluate the performance of the photocatalyst. The result show that the Zn₂GeO₄ nanocrystal is dispersed on the surface of GO uniformly, and compared with pure Zn₂GeO₄,the photocatalytic activity of the Zn₂GeO₄/GO composite is obvious enhanced. When the mass of GO is 5%, the degradation of Rhodamine B is up to 95.21%, and after reused for five times, the photocatalysis still exhibits a better photocatalytic activity. The Zn₂GeO₄/GO nanocomposite photocatalyst possess excellent reusability.（4） A series of g-C₃N₄/Zn₂GeO₄ nanocomposites were fabricated by two-step solvothermal processes. The composites were characterized by TEM, XRD, FTIR, X-ray XPSand ultraviolet–visible spectroscopy（UV-Vis）. The UV-Vis shows that the spectral absorption range of g-C₃N₄/Zn₂GeO₄ nanocomposites is markedly enhanced, and it appears obvious red shift. The photocatalytic performance of the g-C₃N₄/Zn₂GeO₄ was improved obviously when degrade RhB under visible light, and it is 3-6 times much higher than that of pure Zn₂GeO₄.