One-step preparation and photocatalytic performance of vanadium doped TiO<inf>2</inf> coatings

Abstract

In this paper, we have investigated one-step preparation of vanadium doped TiO2 coatings formed by plasma electrolytic oxidation (PEO) of titanium in electrolyte containing 10 g/L Na3PO4·12H2O + 0.5 g/L NH4VO3. The morphology, phase structure, and elemental composition of the formed coatings were characterized by atomic force microscopy (AFM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) techniques. Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) was employed to evaluate the band gap energy of obtained coatings. Vanadium doped TiO2 coatings are partly crystallized and mainly composed of anatase phase TiO2, with up to about 2 wt% of vanadium present in the surface layer of the oxide. The valence band photoelectron spectra and UV-Vis DRS showed that vanadium doped TiO2 coatings exhibit notable red shift with respect to the pure TiO2 coatings. The photocatalytic activity was evaluated by monitoring the degradation of methyl orange under simulated sunlight conditions. Photocatalytic activity of vanadium doped TiO2 coatings increases with PEO time. Prolonged PEO times result in higher roughness of obtained coatings, thus increasing surface area available for methyl orange degradation. Vanadium doped TiO2 coatings obtained after 180 s of PEO time exhibit the best photocatalytic activity and about 67% of methyl orange is degraded after 12 h of irradiation under simulated sunlight.