An investigation on the photocatalytic activity of sub-stoichiometric TiO2-x coatings produced by suspension plasma spray

Abstract To enhance the photocatalytic activity, sub-stoichiometric TiO2-x films were coated on stainless steel substrates by Suspension Plasma Spraying. Because the TiO2 particles are exposed to high temperature during deposition by plasma spray, TiO2-x coating are typically produced. To achieve different levels of oxygen vacancies, as-sprayed TiO2-x coatings were annealed at four different temperatures for 48 h in air. In this work, the degradation of methylene blue was performed to evaluate the photocatalytic activity under visible light. The results indicated that oxygen vacancy positively affects the photocatalytic activity of TiO2-x by introducing some energy levels into the bandgap of titania. Moreover, these energy levels could act as traps for photo-excited holes and electrons, reducing the recombination rate of charges, thus improving the photocatalytic activity under the visible lamp. Additionally, coatings were analyzed by X-ray diffraction, confocal laser microscopy, scanning electron microscopy, Raman spectroscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and UV-visible spectroscopy.