纳米ZnO可见光催化活性的改善及其降解性能

由于半导体ZnO禁带宽度较宽,因而其可见光催化活性较差。本文分别采用N掺杂、碳包覆、贵金属修饰以及半导体复合等方式来改善纳米ZnO的可见光催化活性,并以罗丹明B为降解污染物,对比了不同材料可见光催化降解有机污染物的效率。研究结果显示以氨水为氮源,通过水热法制备的氮掺杂N-ZnO光催化剂,相比于纯ZnO,对可见光吸收增强。采用葡萄糖水热碳化法所制备的C@N-ZnO样品则对有机污染物具有强的吸附能力,贵金属沉积所获得的样品Au/C@N-ZnO与半导体复合所制备的复合结构CdS/Au/C@N-ZnO在可见光区域具有更强的吸收能力。稳态和瞬态荧光光谱显示氧缺陷、贵金属沉积以及半导体复合形成异质结可有效提高光生载流子的分离效率,从而提高催化剂的光降解效率,并对催化机理进行了初步探讨。可见光催化降解罗丹明B结果显示CdS/Au/C@N-ZnO样品的反应速率是纯ZnO的6.7倍。

Improvement of visible light photocatalytic activity of nano ZnO and its performance for organic pollutants degradation

Due to its wide band gap,the semiconductor ZnO has poor visible light photocatalytic activity.In this paper,N-doping,carbon coating,noble metal modification and semiconductor coupling are used to improve the visible light photocatalytic activity of ZnO.The efficiency of photocatalytic degradation of organic pollutants is compared by different materials with Rhodamine B as degradation pollutant model.The results show that the visible light absorption of N-ZnO photocatalyst prepared by hydrothermal method is enhanced in contrast to that of pure ZnO.The C@N-ZnO sample prepared by hydrothermal carbonation of glucose exhibits strong adsorption capacity for organic pollutants.The Au/C@N-ZnO sample obtained by precious metal deposition and CdS/Au/C@N-ZnO prepared by semiconductor coupling show the further enhanced absorption capacity in the visible light region.Photoluminescence and transient fluorescence spectra demonstrate that oxygen defects,precious metal deposition,and semiconductor coupling can effectively improve the separation efficiency of photogenerated carriers,thereby improving the photodegradation efficiency of the photocatalysts.The photocatalytic mechanism is also discussed.The reaction rate for Rhodamine B degradation over CdS/Au/C@N-ZnO is 6.7 times of pure ZnO.