Role of Phase Content on the Photocatalytic Performance of TiO2 Coatings Deposited by Suspension Plasma Spray

In this work, suspension plasma spraying (SPS) with different hydrogen (H-2) flow rates was employed to produce TiO2 coatings with various phase contents, oxygen contents, and roughnesses. To eliminate the role of the morphology and oxygen content on the photocatalytic activity, all coatings were polished to reach the same roughness followed by heat-treatment at 550 degrees C in air for 48 h. Then coatings were analyzed by X-ray diffractometer (XRD), confocal laser microscope, scanning electron microscope (SEM), UV-visible spectrometer, Raman microscope, and thermogravimetric analyzer. The XRD data indicated that the percentage of anatase decreased as function of H-2 flow rates, and almost 46% of anatase transformed to rutile during SPS process at the highest H-2 flow rate. Moreover, the photocatalytic performance was evaluated by monitoring the degradation of methylene blue under visible light irradiation, and the results indicated that anatase phase positively enhances the photocatalytic activity of TiO2 coatings.