Synthesis of neutral SiO ₂ /TiO ₂ hydrosol and its photocatalytic degradation of nitric oxide gas

Abstract

A neutral transparent SiO2/TiO2 composite hydrosol was prepared by a coprecipitation-peptisation method using titanium tetrachloride and SiO2 hydrosol as raw materials. The prepared SiO2/TiO2 hydrosols were characterised by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The evaluation of photocatalytic activity for nitric oxide degradation showed the optimal weight ratio of SiO2/TiO2 is around 1.5. After heating at 700°C for 1 h, the prepared SiO2/TiO2 hydrosol exhibits much higher photocatalytic activity than the commercial TiO2 materials, Degussa P25 and ONID TH. The presence of Ti–O–Si bond in the composite hydrosol results in its good thermal stability. The prepared transparent SiO2/TiO2 hydrosols were stable without agglomeration or gelation after storage at room temperature for over 1.5 years. The neutral SiO2/TiO2 hydrosol could be used as the coating material applying for glass or ceramic building materials which must be treated at high temperature.