Preparation of the transparent TiO2 filM photocatalyst and its use for the photodegradation of VOCs

A TiO2 transparent thin film photocatalyst was prepared for the photodecomposition of VOCs under photo-irradiation with sunlight. A precursor solution for the transparent TiO2 film photocatalysts was prepared using a mixture of alpha-terpineol and hydroxypropyl cellulose (Mw = 80000). The transparent films were prepared by a dip coating method. The maximum thickness of the obtained transparent film was 4.4 mum. The specific surface area was around 80 m(2)/g. The crystallinity of TiO2 film was of anatase alone. Acetaldehyde (1000 ppm in air, 50% relative humidity) was photodecomposed by the transparent TiO2 film photocatalyst. The photocatalytic activity of the films increased with an increase in the film thickness up until 2 mum, and stoichiometric CO2 formation could be observed. Maximum photocatalytic activity of the film was higher than the reference powder P25 photocatalyst. However, the photocatalytic activity at over 2 mum thickness of the film decreased, while the amount of CO2 formed was lower than the stoichiometric ratio. In the case of an excess thickness in the film, the excitation light could not reach the deep layer of the film, and therefore, the intermediate(s) formed from acetaldehyde adsorbed to that layers unless reoxidized to CO2.