The effect of different preparation conditions on the photocatalytic activity of TiO2·SiO2/beads

A photocatalyst based on TiO2·SiO2/beads was prepared by the method of dip-coating, which used hollow glass microbeads as the supporter and titanium tetraisopropoxide[Ti(iso-OC3H7)4] and ethyl silicate as the raw materials. The effects of various factors such as heat treatment temperature, heat treatment time, specific surface area and the amount of SiO2 on the photocatalytic activity of TiO2·SiO2/beads were investigated. The results showed that the best heat treatment condition for TiO2·SiO2/beads is 650 °C for 5 h. For the photocatalytic activity, there is an optimum range of heating temperature and an optimum heating time at each heating temperature. Apart from heat treatment temperature and time, the amount of SiO2 also influences the photocatalytic activity of TiO2·SiO2/beads. The optimum amount of SiO2 is 0.20(molecular fraction). An addition of SiO2 not only raises the adsorbability of the photocatalyst, but also inhibits the temperature effects at which anatase TiO2 transforms to rutile TiO2, and prevents the growth of TiO2 crystal grain. The specific surface area of the photocatalyst decreases with the increase of the heat treatment temperature and time. Although the crystal forms of the photocatalyst remain the same, the photocatalytic activities differ because of the different heat treatment temperatures and times. It is known from the results that heat treatment not only influences the specific surface area of the photocatalyst, but also influences the surface defects and active sites.