氮、银共掺杂TiO2可见光催化剂的制备及表征

Preparation and characterization of nitrogen and silver co-doped TiO2 nanocatalyst for visible light photocatalysis

采用改进的溶胶-凝胶法制备N,Ag共掺杂TiO2光催化剂。利用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-Vis)等表征手段对光催化剂物化性质进行表征。结果表明:N元素以取代的方式掺入到TiO2晶格之间,但不能抑制催化剂晶粒长大,而Ag元素的加入抑制晶粒生长;N,Ag共掺杂TiO2禁带宽度降幅最大。苯酚光催化降解实验表明,改进的溶胶-凝胶法制备的催化剂光催化效率明显高于沉淀法制备的催化剂,在紫外-可见光照射120 min后,N,Ag共掺杂TiO2的光催化效率达到51.3%;在可见光照射360 min后,光催化效率能够达到51.7%,可见光响应并不以牺牲其紫外活性为代价。其原因是N,Ag共掺杂不仅可以降低TiO2的带隙,将其吸收阈值调控至可见光区域,而且增加了催化剂的氧空位浓度,显著增强了催化剂对可见光的响应,从而提高可见光催化降解效率。

Nitrogen and silver co-doped TiO2 photocatalytic material was prepared by improved sol-gel method.Physiochemical properties were characterized by means of X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and ultraviolet-visible diffuse spectroscopy(UV-Vis).The results show that nitrogen doping is substituted into TiO2 lattice,but catalyst grain growth cannot be inhibited.Due to the addition of Ag element,catalyst grain growth is inhibited.Greatest band-gap narrowing occurs due to nitrogen and silver co-doping.The experiments of photogradation of phenol show that photocatalytic efficiency of catalysts prepared by the improved sol-gel method is significantly higher than that of catalysts prepared by the impregnation method.Under UV-visible irradiation for 120 min,the efficiency of nitrogen and silver co-doped TiO2 is 51.3%,and the efficiency is 51.7%under visible light irradiation for 360 min.Fortunately,visible photocatalytic activity is not realised at the cost of UV activity.Nitrogen and silver co-doping not only reduces band gap of TiO2,but also adjusts its absorption threshold to visible region.Simultaneously,oxygen vacancy concentration of catalysts increases and the response of catalysts to visible light significantly enhances,hence photocatalytic activity of nitrogen and silver co-doped TiO2 enhances.