Chorna N. Influence of metal ions doping on the structure and photocatalytic properties of nitrogen-containing titania films

The thesis is devoted to the creation of the photocatalytically active materials based on titania modified by metal ions (zinc, zirconium, iron) and non-metals (nitrogen) to create the effective catalysts under visible light. The influence of the methods and synthesis conditions, as namely nature of the metals, dopant content, ratio of the gas mixture, gas pressure and temperature treatment on the optical, structural and photoelectrochemical properties of nanosized titanium dioxide films. The chemical state of the elements, phase composition and photocatalytic activity are investigated. As shown by X-ray photoelectron spectroscopy, the use of urea in sol-gel synthesis facilitated the nitrogen incorporation in the semiconductive structure in the form of interstitial atoms; accumulation of metal ions on the surface of nanomaterials as a result of complex compound formation during sol aging; acceleration of crystallization rate of certain photocatalytic active phase and formation of the adsorption sites leading to the increased photocatalytic activity. Formation of landauite (Fe2Ti2O7) and pseudobrookite (Fe2TiO5) phases at relatively low temperature (450 °C) without crystallization of individual metal oxides is fixed. The influence of metal ions on the nitrogen incorporation efficiency during pulsed laser deposition is established. Due to the larger zirconium ionic radius than the titanium one, titania lattice deformation occurs resulting in effective substitutional nitrogen incorporation. It is proposed a model of TiN formation at low gas pressure and lower (450 °C) than usually used temperatures. The optimal parameters of the doped titania synthesis procedure allowing to obtain the multicomponent catalysts with higher stability and efficiency in the photocatalytic processes of toxic dichromate ions reduction and tetracycline hydrochloride destruction under UV and visible light comparing with pure TiO2 is experimentally established. N/TiO2, N/Fe/Ti, Fe/Ti (sol-gel method) and 10ZrTiN5C1 (PLD) films can be recommended as versatile photocatalysts under solar irradiation due to their high photocatalytic activity of under both UV and visible light as proven by photocatalytic investigations of dichromate ions reduction and tetracycline hydrochloride oxidation.