Influence of growth parameters on the properties of TiO₂ films prepared by anodic spark oxidation method and photocatalytic degradation of methylene blue

Porous titanium dioxide (TiO₂) coatings were prepared on the pure titanium substrate by anodic spark oxidation (ASO) method in electrolytes containing various concentrations of sulfuric acid. The crystal phase, surface morphology, chemical composition, and optical property of the TiO₂ films were analyzed by using XRD, SEM, XPS, and UV-vis spectroscopy. The photocatalytic activity is evaluated by the decomposition of methylene blue (MB) aqueous solution under UV light irradiation. It is found that the electrolyte concentration plays an important role in the properties and characteristics of the TiO₂ coatings. The results show that TiO₂ films consist of primarily the rutile phase with altering fraction depending on the electrolyte concentration without any heat treatment. The results demonstrated that there were formed too many sub-micron and nanopores of TiO₂ neighboring to the micropores. TiO₂ layer anodized in 0.75 M H₂SO₄ exhibited much higher photocatalytic activity than the other films. The results imply that anatase-rutile mixed TiO₂ coatings can be successfully used for the photocatalytic degradation of organic pollutants.