热处理对Ag-ZnO异质结构光催化性能的影响

Influence of Heat Treatment on Photocatalytic Activity of Ag-ZnO Heterostructure

用溶胶-凝胶法制备纯ZnO和Ag修饰Zn O复合光催化剂,并分别对其进行了400℃、450℃、500℃保温2 h的热处理。使用XRD、SEM、TEM、XPS、PL、BET等手段对其进行了表征。结果表明,纯ZnO和Ag修饰ZnO均为六方纤锌矿晶型,Ag颗粒沉积在ZnO表面形成了Ag-ZnO异质结构。以罗丹明B为目标污染物研究了样品的光催化活性。结果表明,热处理温度对纯ZnO的光催化性能的影响较大,在450℃热处理后光催化效果最佳;热处理温度对Ag修饰ZnO的光催化性能没有显著的影响;Ag修饰ZnO比纯ZnO的光催化活性均有所提高,因为Ag修饰提高了ZnO表面羟基的含量并抑制了光生电子与空穴的复合。在500℃热处理后Ag修饰ZnO对罗丹明B的60 min降解率达到98%,其反应速率常数为0.063 min-1。

The pure ZnO and Ag-modified ZnO composite photocatalysts were prepared by sol-gel method and subsequently heat treated at 400℃,450℃and 500℃respectively for 2 h.The samples were characterized by XRD,SEM,TEM,XPS,PL and BET,respectively.The results show that both pure ZnO and Ag-ZnO are hexagonal wurtzite crystal structures.Ag particles deposit on the surface of ZnO,forming Ag-ZnO heterostructure.The photocatalytic activity of samples was assessed through the degradation of Rhodamine B.The results show that the heat treatment temperature has a great influence on the photocatalytic performance of pure ZnO,while the pure ZnO annealed at 450℃exhibits the best photocatalytic activity.However,the annealing temperature has negligible impact on the photocatalytic activity of Ag-ZnO and all of the Ag-ZnO samples show better photocatalytic activity than that of the pure ZnO.The enhancement in photocatalytic activity of Ag-ZnO can be attributed to the effect of suppressing the recombination of photogenerated pairs and the increase of surface hydroxyl content.The degradation rate of RhB for the Ag-ZnO annealed at 500℃is 98%after 60 min and the reaction rate constant is 0.063 min-1.