Find in Library

Among various methods of improving visible light activity of titanium(IV) oxide, the formation of defects and vacancies (both oxygen and titanium) in the crystal structure of TiO₂ is an easy and relatively cheap alternative to improve the photocatalytic activity. In the presented work, visible light active defective TiO₂ was obtained by the hydrothermal reaction in the presence of three different oxidizing agents: HIO₃, H₂O₂, and HNO₃. Further study on the effect of used oxidant and calcination temperature on the physicochemical and photocatalytic properties of defective TiO₂ was performed. Obtained nanostructures were characterized by X-ray diffractometry (XRD), specific surface area (BET) measurements, UV-Vis diffuse reflectance spectroscopy (DR-UV/Vis), photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy. Degradation of phenol as a model pollutant was measured in the range of UV-Vis and Vis irradiation, demonstrating a significant increase of photocatalytic activity of defective TiO₂ samples above 420 nm, comparing to non-defected TiO₂. Correlation of EPR, UV-Vis, PL, and photodegradation results revealed that the optimum concentration of HIO₃ to achieve high photocatalytic activity was in the range of 20–50 mol%. Above that dosage, titanium vacancies amount is too high, and the obtained materials’ photoactivity was significantly decreased. Studies on the photocatalytic mechanism using defective TiO₂ have also shown that ^•O₂⁻ radical is mainly responsible for pollutant degradation.