Study On The Preparation Of One Dimensional ZnO Nanowire And Its Photocatalytic Application

Recently, the applied research and industrialization of nanoscience and nanotechnology has developed into various production fields. The fabrication and applied research of nanostructured ZnO has received significant interest. Nanostructured ZnO is considered to be one of the most promising high effecitive and low cost photocatalyst. It can be used in the degradation of organic contaminants and mineralizated pollutants. In this paper, great quantity of ZnO nanowire has been fabricated by a carbothermal reduction method. In addition, the photocatalytic performance of ZnO nanowire toward the degradation of methylene blue was initially explored. The main contents of the study are as follows:(1) ZnO nanowire with diameters between 20 nm and 50 nm was prepared by carbothermal reduction method in quartz tube furnace under the temperature of 1150 oC. The source material is a mixture of ZnO powder and graphite powder with a weight ratio of 1:1. The carrier gas is a mixture gas of N2(4.5L/min) and air(0.8~0.9 L/min). The morphology of ZnO nanowire was observed by scanning electron microscopy. Catalyst grains can not be found on both ends of the prepared ZnO nanowire, which indicates the growth mechanism of Zn O nanowire follows Vapor-Solid mechanism. The uniformity analysis results showed that the prepared ZnO nanowire has good uniformity. Most of the diameters of Zn O nanowire are between 25 to 45 nm. The average diameter of the prepared Zn O nanowire is about 33 nm from Gaussian fitting method. Bet surface area measurement was used to characterized the surface area of the prepared ZnO nanowire. The BET surface area of the prepared ZnO nanowire is about 14.92 m2/g. The crystal structure of ZnO nanowire was characterized by X-ray diffraction pattern. The optical properties and the defects of ZnO nanowire was measured by photoluminescence spectroscopy and Raman spectroscopy. The results demonstrated that the diffractrion peaks of ZnO nanowire is in good agreement with the standard diffraction peaks of standard JCPDS card of 65-3411. The prepared ZnO nanowire belongs to hexagonal wurtzite structure. Lattice dislocations and stacking fault defects are not observed in the lattice structure of ZnO nanowire, which shows that the prepared Zn O nanowire has less defects. The crystal structure of ZnO is nearly perfect. Raman spectroscopy characterization results indicates that there existed lots of interstitial Zinc atoms and oxygen vacancies, which facilitates the photocalytic performance of ZnO nanowire.(2) The photocatalytic performance of ZnO nanowire was evaluated toward the photodegradation of methylene blue(MB). Experimental results show that the prepared ZnO nanowire is an excellent photocatalyst in the photodegradation of organic contaminants. The photodegradation of MB over the prepared ZnO nanowires proceeded through the pseudo-first-order kinetic reaction. The value of k, which is the photodegradation rate constant, was fitted to be about 1.86 h-1.(3) Cu2ZnSnS4 showed high photocatalytic efficiency toward methylene under UV irraddiation. A 50 ml solution of methylene orange was degraded by 50 mg Cu2 Zn Sn S4 in half an hour under UV irraddiation. However, Cu2 Zn Sn S4 showed low photocatalytic efficiency toward methylene under visible light irraddiation. By adding small amount of H2O2, Cu2 ZnSn S4 showed high photocatalytic efficiency. A 50 ml solution of methylene orange was degraded by 50 mg Cu2ZnSnS4 and small amount of H2O2 in two hours under visible light irraddiation.