Synthesis And Properties Of TiO₂ Based Photocatalytic Films

Photocatalytic technology is an efficient,safe,and environmentally friendly technology for environmental purification.With the aggravation of water pollution in recent years,the research on the degradation of organic pollutants utilizing sunlight has become the focus in the field of environmental science,photochemistry,materials science and electrochemistry.At present,the main methods to enhance the photocatalytic property include reducing the recombination of photogenerated electron-hole pairs,broadening the light response range of photocatalyst,increasing the light trapping capacity of photocatalyst and improving the specific surface area of catalytic materials.Among numerous photocatalysts,TiO₂ has attracted scientists,extensive attention for its good stability and excellent photocatalytic activity.While,TiO₂ is a semiconductor with wide band gap?3.0 eV-3.2 eV?,which has response to only UV light.In this paper,a series of TiO₂ based photocatalytic films were prepared by composite crystal structure construct and semiconductor composite to inhibit the recombination of photogenerated electron-hole pairs and broaden the range of light response.Photocatalytic properties of films were investigated by degradation of methylene blue solution.First,the TiO₂ film layer was prepared on the glass slide by an improved Czochralski method.TiO₂ nanorod arrays were successfully grown by hydrothermal method on the surface of the as-prepared TiO₂ film.The samples were characterized by XRD,SEM,AFM,UV-Vis spectra.It shows that the films are in accordance with anatase TiO₂ structures,which has the characteristics of uniform surface,high transmittance and well adhesion.The TiO₂ nanorod arrays are in agreement with rutile TiO₂.Consequently,a heterostructure of stratified structure was formed.Compared with rutile TiO₂ films,anatase TiO₂ films and P25 films of approximate thickness,the photocatalytic activity of the composite sample is obviously higher.The two different crystalline phases formed heterojunction on the contact surface and the electrons move directionally under the influence of the built-in electric field,which effectively inhibits the recombination of photo-generated electron-hole pairs and enhance the photocatalytic activity of composite crystalline TiO₂.Second,ordinary glass substrate was replaced by FTO glass.FTO based composite crystalline TiO₂ thin films was prepared by similar methods.The composite film grown on FTO glass substrate has better photocatalytic activity due to the conductivity of FTO,which can effectively transfer the electrons and separate the photogenerated electron-hole pairs in photocatalytic material.Finally,the BiOI was modified on the surface of the composite TiO₂ samples by alcohothermal method and electrochemical deposition respectively.The effect of BiOI deposition was investigated.The composite TiO₂ films modified with BiOI had strong photocatalytic activity under visible light,mainly due to the narrow band gap?1.8 eV?of BiOI,which improved the range of light response and the activity of photocatalytic.