The Preparation And Photocatalytic Performance Of ZnO-Nanowires-Based Composited Nanomaterials

With the rapid development of nano-science technology, ZnO nanowires have become a kind of photocatalyst which had advantages of high photocatalytic performance, low cost, environmentally friendly and no pollution. However, some deficiencies of ZnO nanowires, such as the narrow range of useful wavelength and the high recombination rate of photogenerated electron-hole pairs, still existed in the photocatalytic degradation of organic pollutants in the waste-water. These problems decreased the photocatalytic performance of ZnO nanowires. Until now, the methods to improve the photocatalytic performance of ZnO nanowires are focused on the modification of ZnO nanowires, such as the deposition of noble metals, the doping of metal ions on the surface of ZnO nanowires, and the preparation of composited nanowires, which can be prepared by physical or wet chemical methods. There are a lot of studies about the physical modification methods, such as sputtering, which requires expensive equiptment. On the contrary, with simple process and low cost, wet chemical methods, such as liquid-phase modification method, have a great potential in the modification of ZnO nanowires.Therefore, to improve the photocatalytic performance of ZnO nanowires, this paper this paper adopted the liquid-phase modification method to prepare TiO2/ZnO composited nanowires. The photocatalytic performance of TiO2/ZnO composited nanowires was also studied.The main contents and conclusions of this paper are as follows:ZnO nanowires were prepared by the seed hydrothermal method with mild growth conditions, simple operation and low cost. The effects of growth conditions (concentration of ammonia and PEI, growth temperature and time) on the morphology of ZnO nanowires were studied. This paper concluded that when the growth condition was 25 nM Zn(NO3)2·6H2O, 12.5 mM HMTA,0.3 M NH3·H2O,5 mM PEI, growth temperature of 90? and growth time of 15 hours, the morphology of the prepared ZnO nanowires was satisfing. These nanowires' average length was 14.5 ?m, average diameter was 667 nm, and the aspect ratio was 21.7. Moreover, ZnO nanowires had high verticality and no bottom fusion phenomenon.In order to improve the photocatalytic performance, ZnO nanowires were treated by liquid-phase method of mild growth condition and low cost. TiO2/ZnO composited nanowires were prepared by liquid-phase method at room temperature using ZnO nanowires as the template. The effect of TiO2 deposition time on the morphology of TiO2/ZnO composited nanowires was also studied. This paper came to the conclusion that the optimal TiO2 deposition time for the TiO2/ZnO composited nanowires preparation was 15 min under the conditions of our laboratory.To study photocatalytic performance of TiO2/ZnO composited nanowires, photocatalytic experiments were performed with the methylene blue as the degraded dyes and the 365 nm wavelength ultraviolet lamp as light source. The experiment results showed that the photocatalytic performance of TiO2/ZnO composited nanowires was higher than that of ZnO nanowires. After 10 times of photocatalytic experiments under the same experimental conditions, the degradation rate of methylene blue solution was still higher than 90%. It showed that the TiO2/ZnO composited nanowires not only had higher photocatalytic performance, but also had better stability.