Study On The Photocatalytic Properties Of TiO₂ Hollow Nanofibers Prepared By Electrospinning

TBOT/PVP precursor solution was prepared by sol-gel method,then TiO₂ hollow nanofibers?HNFs?were successfully prepared by a uniaxial electrospinning combined with high temperature calcination method.Pt nanoparticles were loaded to TiO₂ HNFs by UV-ethanol reduction method,the Pt/TiO₂ HNFs photocatalysts were synthesised.The morphologies and properties of the Pt/TiO₂ HNFs photocatalysts were characterized by thermogravimetric analysis?TG?,X-ray diffraction?XRD?,N2 adsorption-desorption,transition electron microscopy?TEM?,UV-Vis diffusion reflectance spectroscopy?UV-Vis DRS?,selected area electron diffraction?SAED?,energy dispersive X-ray?EDX?and X-ray photoelectron spectroscopy?XPS?.The catalytic activity of the prepared photocatalysts were tested by degradation of azo dye Orange ?,the degradation efficiency of Orange ? was evaluated by the decolorization and mineralization efficiencies.First of all,characterizations results show that the TBOT/PVP nanofibers showed significant weight loss in the temperature range of 278-387 oC.With the increase of calcination temperature,the BET specific surface area of TiO₂ HNFs gradually decreased and the pore size increased.The diameter of TiO₂ HNFs was about 200⁶00 nm,the ratio between the inner and outer diameter was about 0.3,and the mean Pt nanoparticles diameter was 2.8 nm.The TiO₂ HNFs were composed of an anatase-rutile mixed phase,with the ratio of ⁷0:30.The Ti,O,C and Pt elements were the components of the photocatalysts.The band gap of TiO₂ HNFs decreased from 3.09 down to 2.77 eV with 2 wt.% Pt loading,and the absorption edge of Pt/TiO₂ HNFs was red shifted to the visible region.Secondly,the effects of the initial concentration of acid orange ?,the amount of catalyst,the initial pH of solution and the calcination temperature of catalyst on the degradation of acid orange ? were investigated in pure TiO₂ nanofiber-ultraviolet photocatalytic system.The results showed that the catalyst concentration=20 mgcat/mgAO?,the initial pH=3,and the catalyst calcination temperature =450 oC were the best reaction conditions.At last,the effects of catalyst concentration,Pt loading,TiO₂ calcination temperature and initial pH on the degradation efficiency of acid orange ? were investigated in Pt/TiO₂ nanofibers-visible light catalyst system.The optimum catalyst concentration was 60 mgcat/mgAO?,the best Pt loading was 2 wt.%,the best calcination temperature was 350 oC,and pH=3 showed best degradation effect.In the whole light irradiation reaction,the catalytic effect of the catalyst was better.The pseudofirst-rate constant?k?of Pt/350-TiO₂ HNFs system was 0.0069 min-1,which was 11.5 and 3.63 times higher than for TiO₂ HNFs and Pt/P25.The catalytic efficiency did not decrease obviously after ten cycles which proved the stability of the catalyst was excellent.By studying the effect of different free radical scavengers on the degradation rate,it was found that ·O₂^-was the main active species for the degradation of Orange ?.