Preparation Of TiO₂Composite Nanofiber And Photocatalytic Properties Research

Global environmental protection has gradually become thehotspot, the degradation of pollutants cause extensive research,effective catalyst is an essential material in pollutant degradationprocess. In recent years, semiconductor as a photocatalyst is usedin photocatalytic reaction, which has made significant progress,among them, the semiconductor TiO2with low cost, non-toxic, highphotocatalytic activity and strong chemical stability can degradethe organic molecules into nontoxic carbon dioxide and water. ButTiO2has two defects, such as large band gap and fastrecombination of electron-hole pairs, which restrict thephotocatalytic activity. Doped-TiO2produce secondary absorptionband, which can reduce the band gap and promote effectiveseparation of electron-hole pairs, leading to higher light efficiency.This thesis adopts La3+, S single-doped and La3+, S co-doped toimprove the photocatalytic activity of TiO2.Compared with the synthesis methods of traditional nanofiber,electrospinning as a simple method with low cost and strongcontrollability makes nanofibers to have large specific surface area,high porosity and strong adsorption, which are applied onphotocatalysis and self-cleaning. In this thesis, tetrabutytitanateand polyvinylpyrrolidone as raw materials adopt electrospinning to prepare the doped-TiO2nanofibers. The structure, morphology andphotocatalytic activity were characterized by XRD, SEM and UV/Visspectrometer. The analysis of1.5mol%La/TiO2nanofibers withdifferent calcination temperature gets optimal calcinationtemperature. With the increase of La3+content, diffraction peaks ofanatase become wide and low, leading to small particle size. DopedLa3+inhibit TiO2phase transition and improve the phase transitiontemperature. Doped La3+can increase the quantiy of oxygenvacancy and surface defects, trap photoelectron, inhibitrecombination of electron and hole and improve the photocatalyticactivity. When molar ratio of La/Ti is1.5mol%, the photocatalyticactivity is the highest.Doped S can inhibit phase transition of anatase to rutile, withthe increase of S content, the width of anatase TiO2(101)diffraction peaks are gradually wide, indicating that doped S caninhibit the growth of TiO2grain. The appropriate S dopant canimprove photocatalytic activity of TiO2, which optimal dopingcontent is1wt%. However, excessive S can destroy the fibermorphology, which present sheet, leading to small surface area andlow photocatalytic activity.Compared with the single-doped TiO2, La3+, S co-doped TiO2nanofibers show the best photocatalytic activity. This may be due tothe La3+, S co-doped synergistic effect, not only reduce the TiO2forbidden band width, separate effectively electron-hole pairs andimprove the quantum efficiency, but also generate more strongoxidizing hydroxyl groups.