氟改性纳米TiO2的制备及其光催化降解甲基橙机理

摘要

采用简易的沉淀-氟化-回流晶化法在低温下制各了氟改性纳米TiO2(F-TiOz),并通过透射电镜(TEM),X射线衍射(XRD),傅里叶变换红外(FTIR)光谱,X射线光电子能谱(XPS)和漫反射光谱(DRS)等表征手段研究了粉末的形貌、晶型、元素形态和光吸收性质.结果表明:实验制得的F-TiO2为椭圆形纳米颗粒,粒径为5-8 nm;氟离子能够有效抑制板钛矿相TiO2的生成,并同时提高锐钛矿相TiO2的晶化度;修饰的氟主要分布在TiO2表面,以化学吸附态为主,并伴有少量的间隙氟.光催化降解甲基橙的实验表明,氟离子改性的TiO2同时具有较高的全谱和可见光催化活性.通过碱洗和焙烧的对照实验分析可知,F-TiO2在可见光下降解甲基橙的机理是源于一种由TiO2表面吸附氟和间隙氟共同增强的染料敏化降解作用.%Fluorine-modified nanosized TiO2 (F-TiO2) was prepared by a facile precipitation-fluorinationreflux method.Characterizations of transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS) were carried out to investigate various properties of the as-prepared F-TiO2 powder.We found that the F-TiO2 particles were small (5-8 nm) and ellipsoidal in shape.The presence of fluorine not only suppressed the formation of a brookite phase, but also improved the crystallinity of the anatase phase.The fluorine atoms were mainly distributed on the surface of TiO2, and existed in both forms of chemical-adsorption and interstitial-doping.Compared to pure titania, the fluorine-modified TiO2 powder showed a much higher methyl orange (MO) degradation efficiency under UV light and under visible light.Through the experiments of alkaline washing and heat treatment, we found that the increased MO degradation rate under visible light irradiation was caused by the enhanced selfdegradation of the dye over the surface-modified TiO2.