Photocatalytic ability of TiO2 porous film prepared by modified spray pyrolysis deposition technique

Abstract

In a spray pyrolysis deposition (SPD) technique, deposition of film material and formation of surface structure are simultaneously occur, therefore, it is suitable for the preparation of microstructure-controlled thin films. We have modified the SPD technique to obtain a TiO2 porous film and the films obtained were evaluated as a photocatalyst. The modified SPD technique consists of consecutive three steps to form nano-porous film. Initially, a mixture of colloidal TiO2 of 40 nm in particle size and Ti-alkoxide dispersed and dissolved, respectively, in propanol was sprayed intermittently onto the heated glass substrate over 70°C, 10 times. Secondly, the same colloidal TiO2 dispersed into water was sprayed similarly onto the above film over 150°C. Finally, this two-times coated TiO2 film was annealed at 500°C for 1 h. Five repetitions of this process gave the porous film with a thickness of 2.5 μm, led to the formation of neck at every contact-point between TiO2 particles. The effective surface area of the film as a catalyst was 8 times larger than that of the non-porous TiO 2 film. Photocatalytic property of the film was evaluated by the decomposition of both aqueous coloring matter and gaseous odorant components under UV irradiation. For example, the reaction coefficients were enhanced from 0.02 min-1 of the non-porous film up to 0.05 min-1 for methylene blue and from 0.05 min-1 up to 0.14 min-1 for dimethyl sulfide. Consequently, the TiO2 porous films prepared by the modified SPD technique have great potential as a useful photocatalyst. © 2009 The Ceramic Society of Japan. All rights reserved.