Preparation Of ZnO And Graphene Oxide And Study On Photocatalytic Activity Of Their Composite Materials

ZnO is a kind of multifunctional semiconductor material with a broad band gap. Because of its excellent physical and chemical characteristics, ZnO has a broad applications in fields such as nanogenerators, gas sensors, solar cells and photocatalysts. Graphene is a layer of carbon atoms with the thickness of a single atom. Its structure is similar to that of carbon nanotube. Since its appearance in2004, it has shown great potential applications.With the continuous development of economy and society and concomitant deterioration of environment, photocatalyst has attracted increasing attentions as a highly efficient and environment-friendly catalyst for degradation of organic contaminants. At present, the most widely applied photocatalyst materials are TiO2and its composites. However, TiO2is expensive and difficult to recycle. ZnO has a similar clearances with TiO2and it is safe, non-toxic and less expensive. At the same time, ZnO has a higher photocatalytic efficiency in degradation of certain contaminants. Therefor ZnO could be a better choice in photocatalysts. In addition, graphene oxide has a large specific surface area which can absorb organic contaminants and its special structure can adjust light absorption range. Therefore, the preparation of high-efficient and cheap complex photocatalyst can be realized through the combination of ZnO and graphene oxide, which is of great significance to photocatalytic degradation of organic contaminants.The main contents and conclusions of this thesis are as follows:(1) The ZnO nanorods with different thickness seed layers on glass substrates have been prepared with low-temperature aqueous solution method. The influence of experimental parameters on morphology and structure of ZnO nanorods has been studied through XRD and SEM. The defect state of ZnO nanorod has been characterized through photoluminescence spectra.The results showed that:with four seed layers, and zinc nitrate and HMT concentration ratio of1:1, the ZnO nanorods obtain the best structure and morphology; With increasing concentration ratio of zinc nitrate and HMT, the uniformity of the ZnO nanorods is getting worse, more and more oxygen vacancy defects and structural defects exist in the ZnO nanorods.(2) In order to study the photocatalytic properties of ZnO, we prepared substrate free ZnO nanorods by self-supporting method. In comparison, we also prepared ZnO nanoparticles by homogeneous precipitation. The XRD and SEM results indicate that the substrate free ZnO nanorods with a highly preferential c-axis orientation, and its diameter is about500nm and5μm in length, with more structural defects. Meanwhile, the average size of ZnO nanoparticles is about50nm, the shape is approximately spherical. Through UV-visible absorption spectrum and photocatalytic experiments, we found that both absorption spectra of ZnO nanorods and nanoparticles have a strong capability of absorbing UV, but they barely absorb visible light. The ZnO nanorod is more capable of absorbing light than ZnO nanoparticles; the degrading abilities of methyl orange under UV irradiation of the two are of little difference and the maximum degrading ratio reaches94%.(3) GO is prepared through the way of Hummers and rGO is reduced through NaBH4, DMAB and ascorbic acid respectively. The results show that NaBH4can reduce GO in the shortest time, but the obtained rGO is easily accumulated and retain low dispersivity and more defects. The DAMB and ascorbic acid reduce GO in a slower speed, but the acquired rGO suspending liquid shows higher dispersivity. Therefor different reductants could be chosen according to different requirements on reducing speed.(4) The substrate free ZnO nanorods and ZnO nanoparticles composite repectively with GO. The ZnO/GO composites are then conducted ultraviolet-visible absorption spectrum photocatalytic test. The results indicate that the compound of ZnO and GO will improve the ability of ZnO to absorb ultraviolet light and visible light; besides, degradation ratio of ZnO/GO composites to methyl orange can reach up to almost100%when exposed to ultraviolet light. Difference of mass ratio in GO and ZnO can exert impacts on light absorption and light catalytic ability of composite materials. With respect to the present test, composite materials with mass ratio of1:20between GO and ZnO exhibit the best light absorption and light catalytic ability.