Characterization and photocatalytic activity of SiO2, FeOx coatings formed by plasma electrolytic oxidation of titanium

SiO2, FeOx coatings were fabricated by plasma electrolytic oxidation of titanium in a silicate electrolyte with an addition of K3[Fe(CN)6]. The structure and elemental and phase compositions of the formed coatings and their surface morphology were characterized by scanning electron microscopy (SEM) in combination with energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). According to XPS, iron is present on the surface of SiO2, FeOx coatings in the form of Fe2O3. Band gaps are equal to 2.6 and 1.4 eV for oxide layers containing 0.6 and 3.4 at.% Fe, respectively. Photocatalytic activity of the coatings was determined by phenol photodegradation in aqueous solution containing hydrogen peroxide under UV-irradiation. In the presence of H2O2, all Fe-containing coatings exhibit photocatalytic activity in phenol degradation. The phenol degradation degree increases along with K3[Fe(CN)6] concentration in silicate electrolyte. The removal of phenol on the SiO2, FeOx coating containing 3.4 at.% Fe reaches 80% after 120 min UV-irradiation. SiO2, FeOx composite oxide layers on titanium are considered to be promising as heterogenic Fenton-like photocatalysts, which can find an application in water purification.