Comparative study on the photocatalytic decomposition of nitrogen oxides using TiO2 coatings prepared by conventional plasma spraying and suspension plasma spraying

Titanium dioxide is one of the most important photocatalysts that allows the environmental purification of various toxic organic compounds in water and removal of harmful air pollutants. In this paper, two techniques of plasma spraying – plasma spraying from an agglomerated nanopowder and liquid suspension plasma spraying – were used to produce thin deposits. The microstructure of coatings was characterized using scanning electron microscopy and X-ray diffraction. The photocatalytic properties of the coatings were evaluated by the decomposition test of nitrogen oxides and compared with the efficiency of the initial agglomerated nanopowder and that of the Degussa P25 powder. Noticeable different behaviours in the photocatalytic tests were observed for coatings performed either from conventional or liquid plasma spraying. The TiO2 deposits realized by spraying of the liquid suspension exhibited higher photocatalytic efficiency. It is found that the plasma spraying of a slurry is an effective method to retain the original anatase phase and prevent the increase of the crystallite size. This new method of modified spraying is proved to be a promising technique to elaborate photocatalytic coatings for the removal of nitrogen oxide pollutants.