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

WO3 and TiO2 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 WO3-TiO2 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 WO3 (monoclinic) and TiO2 (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 TiO2 grows preferentially in the center of the WO3 islands of the deposit underlayer. Photoelectrochemical characterisation of the TiO2/SS 304, WO3/SS 304 and TiO2/WO3/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 TiO2/WO3-coated electrodes were more active not only than TiO2-coated electrodes upon UV illumination but also, than WO3-coated electrodes under visible light excitation.