Photoelectrochemical behaviour of electrodeposited tungsten trioxide and electrosynthesised titanium dioxide single component and bilayer coatings on stainless steel substrates

Abstract

WO 3 and TiO 2 films on stainless steel 304 (SS 304) substrates have been prepared from acidic aqueous solutions of peroxytungstate and titanium oxosulfate, by cathodic electrodeposition/electrosynthesis. Bilayer WO 3–TiO 2 coatings have also been synthesised by consecutive application of the corresponding deposition/synthesis steps. The resulting deposits were annealed at 350 or 400 °C to obtain crystalline WO 3 (monoclinic) and TiO 2 (anatase) coatings respectively, with loadings in the 0.5–2 mg cm −2 range. The deposits had a particulate, “cracked mud” structure, characterised by 5–20 μm large patches. SEM/EDS analysis of the bilayer samples indicated and Auger Electron Spectroscopy confirmed that TiO 2 grows preferentially in the center of the WO 3 islands of the deposit underlayer. Photoelectrochemical characterisation of the TiO 2/SS 304, WO 3/SS 304 and TiO 2/WO 3/SS 304 photoelectrodes was carried out by photovoltammetry and photoamperometry under UV or visible light illumination, in sulfate and oxalate solutions. It was found that bilayer TiO 2/WO 3-coated electrodes were more active not only than TiO 2-coated electrodes upon UV illumination but also, than WO 3-coated electrodes under visible light excitation.