Tuning the photocatalytic activity of nanocrystalline titania by phase composition control and nitrogen doping, using different sources of nitrogen

Titania nanoparticles were synthesized by employing the hydrothermal method and using TiOSO(4) as a titanium source. By varying pH between 0.5 and 1.0 and adding isopropanol to the hydrothermal reaction mixture, different mixtures of anatase, rutile, and brookite were obtained. The samples were also doped with nitrogen at different N concentrations using, respectively, urea, ammonium nitrate, and tripropylamine as nitrogen sources. The samples were characterized by X-ray powder diffraction, field emission scanning electron microscopy, infrared spectroscopy, UV-Vis diffuse reflectance spectroscopy and according to their specific surface area. Additionally, their photocatalytic activity was measured in a gas-solid reactor system. The results show that low pH favours rutile formation, whereas a higher pH yields mixed phase titania polymorphs. Isopropanol addition also favours rutile formation, and boosted the photocatalytic activity of the resulted particles. Contrary to most data in the literature, rutile turned out to be the more active phase in the present investigation. Nitrogen doping, on the other hand, did not contribute to higher photocatalytic activity, but was rather detrimental to it.