The electronic and atomic structures of N doped TiO2 were determined using a combination of hard X-ray photo-electron spectroscopy and first-principles density functional theory calculations. The results revealed that N doping of TiO2 led to the formation of oxygen vacancies and the combination of both N impurity and oxygen vacancies accounted for the observed visible light catalytic behavior of N-doped TiO2.

Oxygen Vacancies in N Doped Anatase TiO2: Experiment and First-Principles Calculations. Rumaiz, A.K., Woicik, J.C., Cockayne, E., Lin, H.Y., Jaffari, G.H., Shah, S.I.: Applied Physics Letters, 2009, 95[26], 262111