Controlled Synthesis And Photo Catalytic Performance Of Nano ZnO Materials With Different Morphology

With the rapid development of chemical industry, the pollution on environment, especially that originating from organic pollutants, becomes more and more serious, so, it is urgent to eliminate organic pollutants. Photocatalytic degradation is a kind of effective techniques for the removal of organic pollutants. Compared with traditional methods such as adsorption, filter and sedimentation, photocatalytic degradation can directly eliminate the secondary pollution without further treatment, largely decreasing the process cost. Under this background, we aim to develop high-performance nano ZnO photocatalytic materials used for the organic pollutants elimination. This dissertation mainly focuss on the following aspects: (1) the systematic optimization of preparation methods of ZnO materials, (2) the careful investigation on the formation mechanisms for the ZnO with different morphology, (3) the evaluation of photocatalytic performance by using the degradation of Rhodamine B as model reaction, (4) the exploration of structure-performance relationship on the basis of multiple characterizations.Firstly, a series of nanosheets-constructed ZnO spheres with novel three-dimensional (3D) fluffy structure were successfully synthesized by a facile one-step solvothermal method. Such special hollow 3D structure makes the ZnO exhibit larger specific surface area. The photocatalytic activity measurement shows that such fluffy ZnO spheres do possess much higher photocatalytic activity than other commonly reported nanostructured ZnO, such as nanoflowers, nanospiraldisks, nanodumbbells and nanorods. Through one-pot synthesis Ag is readily doped on the fluffy spheres, which strongly interacts with them, further improving the photocatalytic performance of ZnO. Based on the properties and characterization results, a special growth mechanism for such fluffy ZnO spheres is proposed, and the photocatalytic reaction mechanism is also discussed.Secondly, to further optimize the preparation methods, the ultrasonic technique was introduced to the preparation process. For comparison, a series of flower-like ZnO materials were successfully synthesized with or without ultrasonic-assistance through changing the dosage of citric acid during hydrothermal synthesis. It is found that both the ultrasonic treatment and the dosage of citric acid have influences on the flower-like structure. The photoluminescence spectra and the photocatalytic activity evaluation show that the employment of ultrasonic treatment during preparation decreases the relative content of oxygen vacancy, thus suppressing green emission and lowering the photocatalytic activity of such flower-like ZnO. However, the ultrasonic treatment can be used for the direct preparation of nano ZnO or Ag/ZnO meterials, whose morphology and photocatalytic activity are obviously influenced by the dosage of Ag⁺ and the ultrasonic frequency. The special growth mechanism of such nano ZnO materials with or without Ag⁺ involvement under ultrasonic treatment wasinvestigated in detail. Thirdly, to increase the specific surface area of ZnO materials, P123 was adopted as the template during preparation, as a result, a series of nano ZnO materials with special morphology and larger specific surface area were successfully synthesized. The effects of the concentration of Zn²⁺ and P123 on the morphology and photocatalytic activity of the ZnO materials were also studied.Finally, a summary about"the Research Methods of Nano ZnO Materials"was made, and the development perspective of nano materials was outlooked.