Abstract:

:TiO₂-SiO₂ composite powders stabilized at high temperature with high photocatalytic activity were prepared using a two-step hydrothermal method, with tetrabutyl titanate and tetraethyl orthosilicate as the materials. The powders were then characterized by means of dynamic light-scattering size analysis, DSC, FT-IR, TEM and XRD. The results of particle size analysis indicate that the composite powders disperse well in a size range of 10 - 30 nm with narrow distribution. DSC results show that the addition of silica greatly improves the high-temperature stability of titania dioxide. Phase analysis results demonstrate that the high-temperature stability of anatase titania becomes better with the increase of SiO₂ content, and that the composite powders with a TiO₂-SiO₂molar ratio of 1 ： 1 maintain as anatase phase after being treated at 1200 ℃for 2h. FT-IR spectra show that there is no Ti-O-Si bonds in the.TiO₂-SiO₂ composite powders before and after the treatment at 800℃ for 2 h. Moreover, according to the degradation of aqueous methyl orange by TiO₂-SiO₂ composite powders under UV irradiation, it is found that （ 1 ） the photocatalysis of the composite powders without heat treatment is similar to that of commercial P25 TiO₂ powders ; （2） the photocatalytic activity of the composite powders after the heat treatment at 800 and 1 000 ℃for 2 h is much higher than that of P25 ; and （3） after the heat treatment at 1200 ℃ for 2 h, the photocatalytic activity of the composite powders becomes poorer.

Key words: titanium dioxide, silica, hydrothermal method, high-temperature stability, photocatalysis