Photodegradation of phenol in water using silica-supported titania catalysts

Titania-coated silica microspheres containing 0.5–3.0 theoretical layers of TiO₂ have been prepared by homogeneous precipitation of TiCl₃. All these χ TiO₂-SiO₂ materials were characterized by X-ray diffraction and FT-Raman spectroscopy. TiO₂ species are distributed on the surface as small anatase crystals and possess a titania-like behavior with a performance equivalent to that of bulk TiO₂ for the photodegradation of phenol. The fraction of used titania is higher than that on bulk catalysts and the absorption of the irradiation by excess titania is prevented. The crystal size of titania particles is critical for optimum performance of the catalyst, since it determines the appropriate surface exposure of titanium sites. A minimum size appears to be required to efficiently mineralize phenol.