Microwave-assisted Synthesis And Microwave Enhanced Photocatalytic Properties Of ZnO And Its Nanocomposites

The different types of photocatalytic nano-materials in this study were prepared by sol-gelmethod combined with temperature-programmed hydrothermal treatment method: ZnOnanoclusters, Ag/ZnO and Ag/ZnO-ZnS nano-composites. The phase structures, morphologyand surface physical and chemical properties were well charactered by X-raydiffraction(XRD), nitrogen adsorption/desorption, transmission electron microscopy(TEM)and scanning electron microscope with energy dispersive spectrometer(SEM-EDS).The results showed that crystal structures of the materials did not change significantly inthe synthesis process supplemented microwave, but at the same time, particle size,morphology and particle size distribution have changed quite drastically. ZnO and itsnano-composite photocatalytic materials were wurtzite crystal structure. ZnO and Ag/ZnO-ZnS system materials have mesoporous structure, and Ag/ZnO system pore structure was notobvious. The silver species in the nano-composite Ag/ZnO and Ag/ZnO-ZnS was metallicAg0. In addition, microwave-assisted synthesised ZnO has three-dimensional sphericalnanoclusters structure, and microwave-assisted synthesised Ag/ZnO after calcination processformed the hexagonal prism structure, moreover, surface area and pore volume ofmicrowave-assisted synthesised Ag/ZnO-ZnS sample was10times and5.7times of thesample without the microwave treatment Ag/ZnO-ZnS, respectively.The photocatalytic activities of the as-prepared materials were studied by the UV andmicrowave-enhanced photodegradation of RhB and other dyes. The results showed that thephotocatalytic activities of ZnO and its nanocomposite prepared by microwave-assistedsynthesised has greatly improved comparing with samples without microwave treatment, andhas microwave enhanced photocatalytic performance. In order to objectively evaluate thecatalytic effect, the commercial P25was compared, and the results showed that withoutmicrowave-assisted synthesized samples were lower than that of P25or close to one, whilethe photocatalytic activities of microwave-assisted synthesised products were higher than thatof P25, indicated that the performance of those catalysts with microwave-assisted synthesiscan be effectively improved.