Effect of surface fluorination on the photocatalytic and photo-induced hydrophilic properties of porous TiO2 films

Porous surface-fluorinated TiO2 (F-TiO2) films were prepared through PEG modified sol-gel method and surface fluorination. The as-prepared films were characterized with XRD, FTIR, AFM, XPS and UV-vis DRS. The effects of surface fluorination on the photocatalytic activity and hydrophilicity of porous TiO2 film were studied by photocatalytic degradation of rhodamine B (RhB) as well as water contact angle (CA) on porous TiO2 film. The results showed that the surface fluorination increased the adsorption of RhB on the porous TiO2 film and enhanced the photocatalytic degradation of RhB. The concentration and pH of NaF solutions affected much the photocatalytic activity of porous TiO2 film. Porous F-TiO2 film prepared in 40 mM NaF solution at pH 4.0 showed the highest photocatalytic activity. Because of its porous structure, the porous F-TiO2 film had original water CA of 22.7°, which is much smaller than that of normal F-TiO2 film. Under UV light irradiation, the water CA of porous F-TiO2 film decreased to 5.1° in 90 min.