Fabrication Of Micro/nano Flower-like ZnO Composites And Their Photocatalytic Performance

With the increase of industrialization in contemporary society, environmental pollution becomes one of the main problems and challenges we have to face. Developing new methods to solve environmental pollution problems is imminent. As a kind of new technology for the treatment of pollution, photocatalytic oxidation technology shows broad application owing to its high efficiency, high photosensitivity and environmental sustainability. Zinc oxide(Zn O), as a potential photocatalysts, have received intensive attention in this area can effectively utilize light energy. During the recent dacades, a variety of Zn O materials with different size and morphology have been prepared. Especially, 3D structures of Zn O show superior photocatalytic properties. Among numerous structures, the 3D porous structure of Zn O has attracted tremendous interest due to superior photocatalytic properties as compared with various low-dimensional Zn O structures. Such a special structure not only avoids the self-aggregation of small particles, but also gives a larger surface area and provides more active sites during the reaction, facilitating the diffusion and mass transportation of organic molecules and increasing the photocatalytic reaction rate. However, the rapid recombination of photo-induced hole–electron pairs has become principle factor affecting photocatalytic efficiency of Zn O photocatalyst. In this work, 3D flower-like Zn O composites have been synthesized and studied their photocatalytic activity. The details are as follows:1. Porous 3D flower-like Ag/Zn O heterostructural composites were fabricated by hydrothermal and photo-chemical deposition methods, without using any pore-directing reagents and surfactants. The obtained samples were characterized with different methods. The experiment results show that the silver nanoparticles successfully load on the surface of assembled Zn O flowers. The photocatalytic degradationexperiments under UV irradiation using Rhodamine B(Rh B) as a model dye were executed. The relative results demonstrate that the photocatalytic activity of Ag/Zn O is obviously improved compared withthe pure Zn O and the commercial Ti O2(Degussa P25), the AZ-15 sample has the highest photocatalyticactivity.2. In the present research, we prepared porous 3D Ce-doped Zn O microflowers using a low temperature-hydrothermal method followed by a heat treatment process for the first time. The effects of cerium doping on the structural and optical properties of Zn O microflowers were also investigated in detail. Finally, the photocatalytic activity of the as-prepared composites is studied, and a possible mechanism of photocatalysis is also discussed and proposed. When the Ce amount increases from 0.25% to 1%, there is more of the dominant Ce4+ to capture electrons, resulting in a greater photocatalytic activity. But, if the amount of Ce4+ ions is higher than the optimum amount(x > 1%), the high concentration of dopant ions act as electron and hole recombination centers and hence the photocatalytic activity decreases.3. In this work, hierarchically 3D flower-like Ag/Zn O composites were prepared through a precipitation method and photochemical deposition technique, which is a simple, low-temperature and eco-friendly synthesis method. The morphologies, structures, and optical and photocatalytic properties of the as synthesized samples were investigated using different techniques. The photodegradation of Rh B was used to evaluate the photocatalytic performance of the materials. The results show that the surface modification of Zn O by silver nanoparticles causes an improvement in the photocatalytic activity both under UV and visible light irradiation. This surface modification induces an increase of the absorption properties of visible light. And a possible mechanism of photocatalysis under UV and visible light was also discussed and proposed.