Fabrication and characterization of photoelectrochemically-active Sb-doped Sn_x-W_(100-x)%-oxide anodes: Towards the removal of organic pollutants from wastewater

Highlights: • Sb-doped Sn_x-W_(100-x)%-oxide coatings were synthesized via a thermal deposition method. • The true electrochemically-active area and the surface roughness of the coatings was found to be composition dependant. • Photocurrent under the anodic bias was found not to depend solely on the band-gap energy. • All the coatings were found to be photoelectrochemically active towards the degradation of phenol red dye. - Abstract: Sn_x-W_(100-x)-oxide coatings (x = 0, 20, 40, 60, 80 and 100) doped with Sb (∼3 at.%) were formed on a Ti substrate by a thermal deposition method in order to evaluate their potential use as electrodes for the photoelectrochemical oxidation of organic compounds. Surface microstructure/morphology and chemical composition of the coatings, as well as their photoelectrocatalytic activities were investigated using electrochemical and surface-characterization techniques. It was found that the surface roughness of the coatings depends on their composition, yielding an average value of R_a = 1.1 ± 0.5 μm. The band gap energy was found to be independent on the coating composition up to the relative W/Sn at. ratio of 4/6, yielding an average value of 3.53 ± 0.05 eV (which corresponds to the band gap of doped SnO₂), but then it decreased for the three coatings with the highest W content, to an average value of 2.56 ± 0.10 eV (which corresponds to the value of pure WO₃). All the coatings were found to be photoactive under the anodic bias. Further, all the coatings were found to be photoelectrochemically active towards the degradation of phenol red dye solution under UV light irradiation. The intrinsic photoelectrocatalytic activity was found to be highest for the Sn_80%-W_20%-oxide electrode coating.