Synthesis of mesoporous ceria/titania thin films for self-cleaning applications

CeO2/TiO2 thin films with a three-dimensional (3D) cubic structure were synthesized. Firstly, mesostructured 3D TiO2 films with high surface area and thermally stable have been prepared. Secondly, CeO2 was deposited on 3D mesoporous TiO2 film by two pathways: (i) cerium nitrate sol in presence of poly(ethylene glycol) was deposited on the prepared mesoporous TiO2 films by spin-coating to obtain 1, 3, and 5 layers CeO2/TiO2 and (ii) the second pathway, for thick CeO2, the prepared mesoporous TiO2 films were suspended into the high concentration of cerium nitrate in presence of poly(ethylene glycol) for 24h with magnetic stirring. FE-SEM images of the mesoporous CeO2/TiO2 films were crack-free and indicated a random worm-like network of the mesopores. The XRD patterns show for all prepared samples only TiO2 anatase phase. At five layers CeO2/TiO2, a weak and diffuse diffraction peak arises, corresponding to (111) plane of cubic CeO2. Methylene blue degradation was conducted to characterize the photocatalytic activity of films and compared with that of commercially available Pilkington Activ™ glass by the determination of their photonic efficiencies. Photonic efficiency of mesoporous TiO2~3.39% is higher than Pilkington Activ™ glass~10 times, probably due to the much larger surface area of the mesoporous films and its high crystallinity. Five layers CeO2/TiO2 films showed two times higher photoactivity for MB oxidation than mesoporous TiO2 film, and its photonic efficiency was found to be ~20 times higher than Pilkington Activ™ glass. Five layers CeO2/TiO2 was fixed after being used repetitively for five times.