Enhanced photoactive and photoelectrochemical properties of TiO2 sol–gel coated steel by the application of SiO2 intermediate layer

• DOI: 10.1016/j.apcatb.2015.03.014
• Publication Date: 2015-03-13T07:16:51Z
• Authors: Juha-Pekka Nikkanen; Elina Huttunen-Sa...; Turkka Salminen; Leo Hyvärinen; Mari Honkanen; Elisa Isotahdon; Saara Heinonen; Erkki Levänen
• Keywords: Titanium Dioxide

Abstract Photocatalysis is a promising solution for purifying air and water from pollutants, yet more efficient photocatalytic materials are needed. A new approach is proposed in this paper for enhancing the photoactive and photoelectrical properties of anatase TiO2 films by applying an intermediate SiO2 film between the TiO2 film and the stainless steel substrate. TiO2 and SiO2 coatings are synthesized by a sol–gel method and the thickness of TiO2 film is varied in order to obtain improved understanding on the role of thickness in photocatalytic and electrochemical performance. The obtained coatings are systematically characterized in terms of microstructure using such techniques as field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy and X-ray diffraction (XRD), that demonstrate, e.g., the anatase phase structure of the TiO2 films. The enhanced photocatalytic properties of SiO2/TiO2 coatings as compared to TiO2 films are verified using methylene blue (MB) discoloration tests, while the improved photoelectrochemical properties are shown by potentiodynamic i–V scans, open circuit potential (OCP) monitoring and electrochemical impedance spectroscopy (EIS). We attribute the beneficial effect of the intermediate SiO2 film on the photocatalytic and photoelectrochemical performance to the high electrical resistance of the SiO2 that imposes a high-energy barrier for electron transfer and, therefore, (partly) insulates the TiO2 film from the substrate and acts as a capacitor for photo-generated electrons under illumination. The presented results show an effective way of enhancing the photocatalytic performance of anatase TiO2 films.