The nitrogen photoactive centre in N-doped titanium dioxide formed via interaction of N atoms with the solid. Nature and energy level of the species

Combined EPR and XPS experiments on N-doped TiO2 obtained via interaction of N atoms with the solid allow to establish the interstitial nature of the dopant and the localized nature of the energy levels associated with the defect. These states lie well below the Ti3+ states generated by thermal reduction of TiO2 and spontaneously drain off electrons from Ti3+ species.