Influence of the OH groups on the photocatalytic activity and photoinduced hydrophilicity of microwave assisted sol–gel TiO 2 film

Abstract

In the present work the influence of the OH groups on the photocatalytic activity and the photoinduced hydrophilicity of microwave assisted sol–gel TiO 2 films was investigated. The prepared TiO 2 films were characterized using XRD and AFM. Furthermore, the surface of the TiO 2 films was examined by help of XPS in order to determine the amount of OH groups before and after UV irradiation at different humidities. The activity of the TiO 2 films was determined using stearic acid as a model compound and the photoinduced superhydrophilicity was investigated through contact angle measurements. The results of this investigation showed that the microwave assisted sol–gel technique produces highly homogeneous and efficient TiO 2 films without the need for heat treatment for crystallization. Based on the conducted experiments it is suggested that the amount of OH groups on the TiO 2 surface highly influence the photocatalytic activity and the photoinduced superhydrophilicity and that the two mechanisms may be closely related. It is suggested that the superhydrophilicity is obtained through a combination of photocatalytic degradation of organic contaminants and surface structural changes in form of an increased amount of OH-groups.