WO 3 /TiO 2 composite coatings: Structural, optical and photocatalytic properties

Abstract WO 3 /TiO 2 and TiO 2 coatings were prepared on titania substrates using facile and cost-effective plasma electrolytic oxidation process. The coatings were characterized by X-ray diffraction, scanning electron microscopy, Raman, UV⿿vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. With increasing duration of PEO process, the monoclinic WO 3 phase became dominant and new monoclinic WO 2.96 phase appeared. The optical absorption edge in the WO 3 /TiO 2 samples, enriched with WO 3 /WO 2.96 phase, was shifted to the visible region. The photocatalytic efficiency of WO 3 /TiO 2 and pure TiO 2 samples was evaluated by performing the photodegradation experiments in an aqueous solution of Rhodamine 6G and Mordant Blue 9 under the visible and UV light. The WO 3 /TiO 2 catalysts are much more efficient than pure TiO 2 under visible light and slightly better under UV light. The improvement of photocatalytic activity in the visible region is attributed to better light absorption, higher adsorption affinity and increased charge separation efficiency.