Comparative study on the photocatalytic behaviour of titanium oxide thermal sprayed coatings from powders and suspensions

This work presents a study of the microstructures and photocatalytic behaviour of titanium oxide coatings obtained by thermal spraying of agglomerated nanopowders and suspensions. Fine TiO₂ Degussa P25 nanopowder, generally considered as the reference material in photocatalytic applications, was used as the material feedstock. HVOF process and suspension thermal spraying were used to prepare photocatalytic titania coatings. The coatings were mainly characterised by means of SEM and X-ray diffraction. The photocatalytic performance was evaluated based on decolouration of the pink dye Rhodamine B and degradation of gaseous acetaldehyde. A lower degree of pollutant degradation was found for deposits prepared by HVOF spraying of granules due principally to the low content of the photocatalytically active phase, i.e. anatase. Complete photocatalytic degradation of the organic compounds was recorded for the suspension-sprayed coatings. Based on the current results, suspension thermal spraying appears to be the better choice for preparing photocatalytically active titanium oxide surfaces for the removal of organic pollutants.