Photocatalytic activity of visible-light-active iron-doped coatings prepared by plasma spraying

This study examines the photocatalytic activity of coatings produced by atmospheric plasma spraying (APS). The applied spraying tools were gas-stabilized (GSP) and water-stabilized (WSP) plasma guns. The TiO2–Fe2O3 powder with and without Na2SiO3 additive was produced as agglomerates suitable for feeding into the plasma jet. The coatings are analyzed by scanning electron microscopy, X-ray fluorescence and X-ray diffraction. Photocatalytic degradation of butane under UV and under visible light, as well as the growth kinetics of the products – carbon dioxide and carbon monoxide – is quantified for all coatings and compared with a pure TiO2 coating. The coatings show a lamellar structure, as it is typical for this process. However, their porosity is rather high. Anatase titania from the feedstock powder is converted into rutile phase in all coatings; whereas the presence of FeTiO3 is detected in the coating without Na2SiO3 made by WSP and metallic iron in the GSP coating. The coating from powder with Na2SiO3 admixture is partly amorphous. This coating is photocatalytically active especially under UV, whereas under visible light it is overcome by the WSP coating. The GSP coating has the best photocatalytic activity under both different radiations.