Synthesis and photoelectrocatalytic activity of Se–WO3 coatings on AISI304 type steel

Abstract

The aim of the current work was to obtain photoactive Se–WO3 coatings on stainless steel and to determine their photoelectrocatalytic activity towards oxidation of some aliphatic alcohols (methanol, ethanol, 2-propanol, 1-buthanol). This work is relevant to developing photocatalytic methods for the oxidative destruction of organic pollutants. Se–WO3 coatings on stainless steel were prepared by electrochemical deposition under potentiostatic conditions. The synthesis was carried out by using 0.1 M Na2WO4 + 0.1 M H2O2 + 0.01 H2SeO3 + 0.3 M HNO3 electrolyte at 291 K. The obtained Se–WO3 coatings were characterized by photovoltammetry and X-ray diffraction (XRD) analysis.

The experimental results show that the most uniform and mechanically stable Se–WO3 coatings were obtained at -0.35 V, the deposition time being 20 min. The incident photon-tocurrent efficiency (IPCE) amounts to 12% at +0.8 V for a Se–WO3 electrode annealed at 673 K. Such coatings consist mostly of the monoclinic WO3 phase, as was evidenced by XRD analysis. The average WO3 crystallite size was calculated to be about 62.6 nm.

An increase in the concentration of the aliphatic alcohols in K2SO4 electrolyte leads to the enhancement of generated photocurrents. An increase in the molar weight of the alcohols causes a decrease in photocurrents. The obtained results show that the kinetics of the photoelectrochemical oxidation of methanol can be described in terms of the Langmuir–Hinshelwood model. The bulk electrolysis experiments revealed that the prepared films are more active than the previously studied TiO2 and Ag / TiO2 films. They are stable and can be used for photoelectrochemical mineralization of methanol.