Synthesis And Photocatalytic Properties Of Nano ZnO And Its Composites

Energy shortage and environmental pollution are the two main challenges for human beings in the future, while photocatalytic water splitting and photodegradation of pollutants have been considered to be an effective way to solve these two problems. When compared with the conventional TiO2, the semiconductor ZnO with a wide band gap has a richer source and a higher quantum efficiency, which is considered to be one of the potential materials to replace TiO2. However, the development of ZnO photocatalyst has been seriously restricted by the fast recombination of photo generated carrier and photocorrosion of ZnO, these two problems must be solved in order to realize the large scale application of ZnO photocatalyst. Herein, we have prepared ZnO nanorods through facile solvothermal method and then loaded Ag nano particles on ZnO nanorods to form Ag-ZnO nanoheterostructure. Furthermore, ZnO-rGO composite photocatalysis were obtained by coupling GO with ZnO nanorods and the photocatalytic performance of these two photocatalysts have been studyed. Main research works are as follows:1. The ZnO nanorods with uniform morphology and good repeatability were prepared by the solvothermal method. Based on the investigation of the effect of morphology and surface defects on the photocatalytic property by different annealing temperature, we found that the main mechanism of carrier recombination is dominated by surface oxygen vancancies as VO×â†'VO¨, known that the Fermi level of Ag locates between these two defects level, we loaded Ag nano particle on ZnO nanorods by photoreduction of Ag+and use the Fermi level of Ag as a fast transfer channel for the photogenerated electrons to transfer from VO× to Ag surface thus promotes the separation of the photogenerated carriers. The surface plasmon resonance effect of nano Ag particles was also used to improve the photocatalytic activity of the composite photocatalyst. Finally we disscussed Ag content on the performance of Ag-ZnO photocatalyst, and it was found that the proper amount of Ag loading could maximize the performance of Ag-ZnO photocatalyst.2. Surface modification of ZnO nanorods has achieved with the aid of silane coupling agent. The positively charged ZnO nanorods was then coupling with various mass contents of negatively charged GO sheet through electrostatic self-assembly and followed by the GO reduction to rGO via hydrothemal treatment to obtain ZnO-rGO composite photocatalysis. Corresponding characterizations of the morphology, structure and photocatalytic properties were performed on the as-synthesized samples and the hard intergrated sample without surface modification, revealing the mechanism of photocatalytic enhancement.3. Through photocatalytic degradation of RhB and phenol by ZnO-rGO composite photocatalyst we disscussed the effect of pollutants surface charge on the performance of photocatalyst adsorption and photocatalytic degradation, and revealing the role of different free radicals on photodegradation of RhB and phenol by adding radical scanvengers. The total organic carbon test further proved the RhB and phenol were degraded to CO2 which provides reference for the application of ZnO photocatalyst in the future.