【作者】 张靖峰；

【导师】 杜志平； 赵永红；

【作者基本信息】 中国日用化学工业研究院 ， 应用化学， 2007， 硕士

【摘要】 采用氨浸法制备了纳米ZnO,并在此基础上通过掺杂贵金属Ag和过渡金属离子Fe3+,复合半导体SnO2等手段对其进行了改性,分别制得纳米Ag/ZnO、Fe3+/ZnO和SnO2/ZnO复合光催化剂。利用X射线衍射、N2吸附、X射线光电子能谱和紫外-可见漫反射光谱等方法对所得催化剂的晶型结构、比表面积、表面组成和光吸收性能等进行了分析表征。以壬基酚聚氧乙烯醚(NPE-10)为模型污染物,分别在紫外光和可见光照射下考察了ZnO及其复合物的光催化活性。采用氨浸法在300℃下煅烧2h得到晶型完美的纳米级ZnO,且随着煅烧温度的升高,ZnO晶体粒径逐渐增大,而比表面积则逐渐减小。贵金属Ag掺杂在纳米ZnO中,以Ag0和Ag+两种形式存在,导致纳米Ag/ZnO晶体粒径随Ag负载量的增加而增大,比表面积减小。与纯ZnO相比,0.5%Ag/ZnO样品中Ag3d5/2结合能减小,而Zn2p和O1s结合能增大,Ag/ZnO表面的羟基氧和吸附氧含量增加;吸收光谱发生红移,在可见光区出现表面Ag离子的共振吸收峰。过渡金属离子Fe3+掺杂到纳米ZnO中,以Fe3+、Fe2+和Fe0三种形式存在,Fe元素取代Zn进入ZnO晶格或存在于ZnO晶隙中,致使晶体粒径随Fe3+负载量的增加而减小,比表面积增大。相比纯ZnO而言,0.5%Fe3+/ZnO样品中Fe2p结合能减小,而Zn2p和O1s结合能增大,Fe3+/ZnO表面的羟基氧和吸附氧含量增加。铁元素的存在使ZnO的价带和导带之间产生中间能级,降低了电子激发所需能量,从而使铁掺杂ZnO在可见光区出现吸收。半导体SnO2复合改性纳米ZnO中,Sn以Sn4+形态存在于SnO2晶体和固溶体中,抑制了ZnO的生长,使得晶体粒径随SnO2加入量增加而减小,比表面积增大。负载量为20%的SnO2/ZnO样品较纯ZnO的Zn2p和O1s结合能增大,表面的羟基氧和吸附氧大量增加,加入SnO2可以改变ZnO的能带隙,增强其对可见光的吸收。对NPE-10的光催化降解性能研究表明:在紫外光和可见光照射3h后,0.5%Ag/ZnO能使降解率提高26%和40%、0.5%Fe3+/ZnO能使降解率提高18%和33%、20%SnO2/ZnO能使降解率提高20%和45%。更多还原

【Abstract】 Nano-ZnO and Ag/ZnO, Fe3+/ZnO and SnO2/ZnO were prepared by ammonia immersion method. The crystal structure, specific surface area, surface composition and spectral characteristic were analyzed by X-ray diffraction, N2 adsorption, X-ray photoelectron spectroscopy and diffuse reflectance ultraviolet-visible spectroscopy, respectively. The photocatalytic activity of catalysts for nonylphenol ethoxylates-10 (NPE-10) degradation was studied under the irradiation with ultraviolet light and visible light.The crystal structure of nano-ZnO which was calcined at 300℃for 2h was perfect, and the particle size of ZnO increased and specific surface area decreased with the increasing of calcination temperature.In Ag-modified nano-ZnO, Ag element exists in two forms: Ag0 and Ag+. The particle size of Ag/ZnO increased and its specific surface area decreased with the increase of Ag loading. Compared with the nano-ZnO, the binding energy of Ag3d5/2 in 0.5%Ag/ZnO reduced, but the binding energy of Zn2p and O1s increased; and the contents of adsorbed oxygen and hydroxy oxygen on the surface increased remarkably. The 0.5%Ag/ZnO exhibited red shift in the absorption spectrum, and the resonance absorbing peak of Ag ion appeared in the visible region.In the Fe3+-modified nano-ZnO, Fe element exists in three forms: Fe3+, Fe2+ and Fe0. The particle size of Fe3+/ZnO decreased and its specific surface area increased with the increase of Fe3+ loading because Fe entered the crystal lattice of ZnO superseding Zn. Compared with the nano-ZnO, the binding energy of Fe2p in 0.5% Fe3+/ZnO was reduced, but the binding energy of Zn2p and O1s increased; and the contents of adsorbed oxygen and hydroxy oxygen on the surface increased. The adding of Fe element provided a intermediate energy level between the valance band and the conduction band of ZnO, which can reduced the essential energy of the electron excitation. Thus, it resulted that Fe/ZnO exhibited absorption in the visible region.In the SnO2-modified nano-ZnO composites, Sn element exists in SnO2 crystal with one form: Sn4+. The particle size of SnO2/ZnO decreased and its specific surface area increased with the increase of SnO2 loading because SnO2 had restrained the growing of the ZnO crystal. Compared with the nano-ZnO, the binding energy of Zn2p and O1s in 20% SnO2/ZnO increased, and the content of adsorbed oxygen on the surface increased. The band gap energy of ZnO had been changed and the adsorption of visible light of ZnO was enhanced because of the SnO2 adding.The optimum photocatalytic activity was obtained from 0.5%Ag/ZnO, 0.5%Fe3+/ZnO and 20%SnO2/ZnO, respectively. The extra 26% (40%), 18% (33%) and 20% (45%) degradation rate of NPE-10 could be found under 3h irradiation of ultraviolet (visible light), respectively.更多还原