Synthesis And Characterization Of ZnO And Ag/ZnO Micro/Nanostructures And Their Potocatalytic Activity

ZnO is an important wide-direct band gap (3.37eV) n-type semiconductor with a large exciton binding energy of60meV, which has made it be widely used in the fields of light-emitting devices, solar cells, antibacterial, sensors, catalysis and so on. Recently, it has received more attention as a promising photocatalyst to deal with water pollution owing to its high catalytic efficiency, low cost and environmental sustainability. However, its activity of photocatalysts and utilization rate of sunlight are not yet ideal. Therefore, in this paper, ZnO is studied as the subject, improving photocatalysis performance as the research aim, synthesising different morphologies ZnO and composite materials based on ZnO and investigating their photocatalysis performance as the research content, the details are as follows:(1) ZnO microspheres were fabricated through hydrothermal method, using zinc acetate as raw materials, triethanolamine (TEA) as the precipitant. The effect of the volume ratio of water to TEA and temperature on the morphology of ZnO was systematically studied. And the growth mechanism of ZnO microspheres was studied by investigating its growth process. Finally, the photocatalytic activity of the samples was tested with the photocatalytic degradation of methylene blue. Results demonstrated that the activity of ZnO microspheres was about2times of commercial ZnO.(2) Spindle ZnO and flower-like ZnO were synthesized through changing the rate of zinc acetate to sodium peroxide by hydrothermal method. The effect of morphology on the optical property of ZnO was studied, and the growth mechanisms of spindle ZnO and flower-like ZnO were studied by investigating their growth process. Finally, the photocatalytic activity of the samples was tested with the photocatalytic degradation of methylene blue. Results demonstrated that the activity of flower-like ZnO had higher photocatalytic activity than spindle ZnO.(3)Different morphologies Ag/ZnO composites were successfully synthesized on the basis of as-prepared ZnO by microwave-assisted polyol method. Results demonstrated that the composites were composed of wurtzite ZnO face-center-cubic Ag; Ag/ZnO composites had strong absorption in the UV and visible light range and the absorption band showed some red-shifts compared to the ZnO. Finally, the effect of morphology on the photocatalytic property of Ag/ZnO was studied, and the photocatalytic activity order was as follows:flower-like Ag/ZnO>spindle Ag/ZnO>spherical Ag/ZnO.(4) To spherical Ag/ZnO composites, with the increase of Ag content, the photoluminescence intensity of Ag/ZnO composites decreased firstly and then increased; Ag/ZnO composites exhibit higher photocatalytic activity than ZnO particles; however, the Ag/ZnO composite prepared with AgNO3concentration of0.05M has the highest photocatalytic activity. Because the Ag nanoparticles on the surfaces of ZnO could promote the separation of photogenerated electron-hole pairs, the photocatalytic activity was enhanced.