Paramagnetic centers of photocatalysts based on nitrogen-doped titanium dioxide

Titanium dioxide doped with nitrogen (N-TiO2) was studied by electron paramagnetic resonance spectroscopy. Two types of paramagnetic centers were observed: N-center dot and NO. The concentration of these centers depends significantly on temperature and irradiation with visible and UV light. It was established that the energy levels corresponding to the N-center dot and NO centers are, respectively, 2.3 and 2.0 eV below the N-TiO2 conduction band. These centers are involved in the photooxidation of organic compounds on the N-TiO2 surface.