Microwave-Assisted Hydrothermal Process Synthesis Of Porous ZnO And Their Photocatalysis Properties

In recent years, With China's rapid economic development and rising living standards, environmental issue have attract more and more attention. Especially the organic dye pollutants which have always been an intractable challenge to industrial manufacture, as they can contaminate water and soil, destroy ecological system, and have harmful effects on human health. Therefore, to find an efficient way to degrade the organic dye pollutants has of course great consequences for promoting economic development and social progress.Zinc oxide(ZnO) is an important semiconductor with wide direct bandgap energy of 3.37 eV, and its large exciton binding energy is 60 meV. For the electron excitation under UV light, ZnO possesses great appliance value. it is believed that photocatalytic and many other properties are closely related to the high porosity and specific internal surface area of 3D ZnO porous hierarchical architectures. Therefore, it is still a challenge to synthesis mesoporous Zn O with high internal surface in a controllable way for photocatalysis application. In this paper, we report an efficient approach to synthesis of 3D mesoporous Zn O hierarchical architectures with homogeneous porosity and specific internal surface area as we expected, and its photocatalytic activities was tested.In Chapter 2, we introduced the synthesis process of Zn O. With the assistance of glycine and polyvinyl pyrrolidone(PVP), we synthesized a new structure, mesoporous structured microspherical honeycomb and roselike ZnO, via microwave-assisted hydrothermal process and a calcination procedure. The materials were charactered by the means of powder X-ray diffraction(XRD), low temperature N2 adsorption and SEM. The results show that the monoclinic hydrozincite Zn5(CO3)2(OH)6 and wurtzite phase of ZnO exhibit highly crystalline, and be annealed at 450 ? can obtain a better crystallization. Furthermore, the result of TG-DTA also proved this point. Moreover, morphology of ZnO varies as ionic concentration and the mount of urea varying. The formation process of microspherical honeycomb and roselike ZnO three-dimensional architectures is proposed to be process comprised of hydrolysis, nucleation, formation of nanoparticles, nanoparticles oriented aggregating and nanosheets oriented stackingIn Chapter 3, we carried out photocatalytic experiment in which the degradation of methyl orange(MO) aqueous solution was tested. The result of photocatalytic experiment suggested excellent photocatalytic property of ZnO. Moreover the photocatalytic property is better in acid solution than in alkaline solution, and the degradation Of MO is 92% after 3h. In this Chapter, a comparative study reaction time and mount of catalyst was carried out respectively.