| Up to now,titanium dioxide(TiO2)is the mostly studied semiconductor due to its numerous advantages,including low prices,richness in material resources,non-pollution,good stability and high catalytic activity.However,it still has some limits,such as relatively large band gap(3.2 eV for anatase)and narrow light absorbing wavelength(mainly concentrated in ultraviolet region),which makes them can only use 2%-4%ultraviolet of the sunlight and results in low quantum yields owing to the high combination probability of photo-generated electron and holes.Therefore,these limits greatly hinder widely application of TiO2.In order to solve above problems,in this paper,we used the polymer modified method and noble metal deposition method to modify TiO2.Based on these approaches,both the utilization efficiency of sunlight and separation efficiency between photo-generated electron and holes are improved which lead to the improvement in catalytic activity of TiO2.First,tetrabutyl titanate(Ti(OBu)4)and polyvinylpy-rrolidone(PVP)K-30(Mn=40,000).K-90(Mn=1,300,000)were selected as the source of TiO2 and polymer template,respectively.Anatase phase,rutile phase and mixture of anatase phase and rutile phase TiO2 nanofibers were prepared via electrospining method.The influence of calcination temperature and time on the TiO2 crystalline phase was investigated.The experimental results showed that calcination temperature had great influence for the production of TiO2 crystaline phase in these two systems.The nanofibers obtained from precursor solution in K-90 system was better than that obtained in K-30 system by electrospining method.After the calcination,the morphology of nanofibers obtained in K-90 system also kept better.The as-prepared TiO2 nanafibers had good catalysis activity to Rhodamine B.Next,we prepared TiO2@polyaniline(PANI)composites by in-situ polymerizati-on method.The structures and properties of composites were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),fourier transform infrared spectrum(FT-IR)and UV-Vis Difffuse Reflectance Spectrum(DRS).PANI did not change the crystal form of TiO2,but it made absorbance of TiO2 nano fibers extended to the visible-light region,absorption edges of TiO2 red-shifted and the band-gap reduced.The TiO2@PANI nanocomposite had good catalytic activity in degradation of Rhodamine B.Finally,Ag/TiO2 nanofibers was prepared by photoreduction-deposition method.The morphology and crystalline phase of Ag nanoparticles on the TiO2 nanofibers were controlled by adjusting illumination time and the experimental results showed that the diameter of Ag nanoparticles become bigger with the increase of illumination time.In degradation of Rhodamine B,the catalytic activity of Ag/TiO2 nanofibers was improved due to the introduction of Ag nanoparticles. |
