N-doped hydrogenated titania hollow spheres for photocatalytic applications

The most known and used semiconductor in heterogeneous photocatalysis is nanostructured titanium dioxide, TiO2. Recent studies have demonstrated that the morphology of titania nanoparticles can be modified in hollow spheres, which increase its optical and electronic properties, thus the photocatalytic activity, due to the high surface-to-volume ratio and the effect of void space. Moreover, recent studies have demonstrated that both doping and reduction of TiO2 brings along an increase in photocatalytic efficiency, tuning the band gap of the semiconductor. This modification can promote the absorption in the full solar light spectrum, from visible up to IR region. In this Thesis, TiO2 hollow spheres (THS) were synthesized through a sol-gel template-based technique. Nitrogen doping was performed at different atomic concentration and the band gap was further lowered by following chemical reduction under annealing, obtaining hydrogenated N-doped THS. Different characterization techniques were employed, such as SEM and HRTEM for the morphology of the sample, XRD and Raman spectroscopy for the composition and the crystalline phase, XPS for the electronic structure and UV-Vis spectroscopy for the optical properties and the calculation of the band gap. Eventually, functional properties were investigated in the photodegradation of a dye (rhodamine B), an antibiotic (metronidazole) and a mixture of the two, both under UV light and solar simulated light.