In-flow photocatalytic oxidation of NO on glasses coated with nanocolumnar porous TiO2 thin films prepared by reactive sputtering

Abstract

The magnetron sputtering technique has been successfully employed for the preparation of porous TiO2 thin films on soda-lime glasses by means of an oblique angle deposition strategy. The morphology of the thin layers is affected by the deposition parameters, such as, the angle with respect to the target, applied power, total pressure, oxygen pressure and deposition time. It has been shown that 60–65° angles, lead to a compromise between the porosity, the level of oxidation and the thickness of the film. High total pressures of the deposition process result in less dense coatings of greater porosity. Moreover, the oxygen flow during the deposition process must be carefully adjusted for each set of deposition conditions, in order to achieve an optimum degree of oxidation. The evaluation of coated-glasses in the in-flow photocatalytic oxidation of nitrogen oxide has shown that the presence of a porous film is essential to achieve photocatalytic activity. The best performing coated-glass was able to reduce the NO concentration ca. 20% for 5 h. SEM and TEM images of this film show a microstructure composed of nanometric grains and a tilted columnar structure. Nanocrystal electron diffraction, XRD and Raman spectroscopy have confirmed the deposition of TiO2 anatase.