Photocatalytic Properties And Applied Research Of Multi-modified Titanium Dioxide Film

Titanium dioxide photocatalyst as a kind of high efficiency, low toxicity, greenenvironmental protection material, have received much attention of scientists, they had madegreat progress on the property research and application research. After being irradiatied oflight whose wavelength is smaller than387nm, titanium can be excited to producephotogenerated electron-hole pairs. These electron-hole pairs have strong redox properties sothey can react with the organic pollutant on the surface of titaniam via a series of redoxreaction, in which process organic pollutant is finally degradated to be nontoxicmicromolecules, such as CO2, H2O, etc. The reaction was favoured by many scientists due toits low consumption, green pollution-free. However, the practical application of titaniumoxide has been limited by his two shortcomings. First, titanium oxide has a high band gapenergy (Eg=3.2ev), which means that only under irradiation of ultraviolet light, can thetitanium create electrons (e-) and holes (h+). But the proportion of the UV light in sunlight isnot as much as5percent. Therefore, its utilization of sunlight is very low, namely in thesunlight, its photocatalytic activity is low. Second, the photogenerated electrons and holes arevery active and their recombination can happen easily, which reduce the photocatalyticactivity. Therefore, how to widen the optical response range of the titanium dioxide and lowerthe recombination rate of photo-generated electrons and holes, become two breaches toincrease the photocatalytic activities and the applications area of titanium dioxide.Because of the above problems, we had modified on the titanium oxide. Many methodshave been developed for modifying the titanium dioxide. And the methods of ion-surfacedoped and silica modified are used in this article. Then we will make further attempt to widenthe application range of modified composite films.This paper mainly includes the following four parts:(1) Preparation and property study of TiO2/SiO2filmsThis study takes tetrabutyl titanate as titanium source, four ethyl silicate as silicon sourceto make TiO2colloid and SiO2colloid by sol-gel method, when being aging well, two kinds ofcolloid would be mixed at a certain percentage, then the films are pulled on glass matrixubstrates by using dip-coating method, using the method of the additive doped ions at the surface. and finally, after being high temperature roasting, we will get nano TiO2/SiO2composite films which has photocatalytic activities. The optimum concentration and codopedratio of I、Fe、Ca、Co、F ions are determined by the degradation of ions doped TiO2/SiO2filmsfor the dyes, and based on the optimum concentration or codoped ratio, the films can be usedfor the terramycin and formaldehyde. The experiment results tell that, the photocatalyticactivities of ions codoped modified films have been enhanced obviously, and the range oflight response is also increased.And it is effective in the degradation of terramycin andformaldehyde.(2) Characterization of TiO2/SiO2filmsThe ultraviolet-visible absorption spectroscopy (UV-Vis), X-ray diffraction (XRD),simultaneous thermal analysis (DTA/TG), field emission scanning, photoluminescence (PL)spectroscopy, and N2adsorption-desorption measurements (BET) are used to characterizestructure of the surface and Photocatalytic behaviors of the composite films, the reactionmechanisms of codoped films are also probed Research finds that among three crystals ofTiO2, only anatase has the photocatalytic avtivity. The experiment results show that, whenmodified by dopig with ions and SiO2semiconductor, the crystals of rutile and brookitealmost disappeared, show the pure anatase phase. In addition, modifying can inhibit thesurface agglomeration of TiO2films, leading the surface becomes uniformly and smoothly,and can also enhance the specific surface area of the films.(3) The exploration of photocatalysis mechanismAfter SiO2composite, the growth of grain and the transformation from anatase to rutilephase are obviously inhibited, and the surface area and adsorption capacity of thin films wereincreased. At the mean well, SiO2and TiO2can react to creat the lewis acid on the compsitefilms’ surface, which resulting in an increase in the number of hydroxyl groups on the surface,enhanced water absorption. And ion doping can narrow band gap width by different level, soas to improve the long-wavelength absorption of sunlight, at the same time, the incorporationof cation and anion can attract light raw electrons or holes, thus control the recombination ofelectrons and holes.(4) To expand the field of applicationUse the modified TiO2/SiO2composite films to degradate emerging contaminants on the basis of the degradation of organic dyes, such as antibiotic medicines and aldehyde pollutants,to expand the scope of the application in the real world and make it has more practical value.