Role of N Doping in the Reduction of Titania Nanostructures

The effect of N-doping of titania (TiO₂) nanoparticles (NPs) on their reduction through neutral O vacancy (O_vac) formation is investigated using all electron density functional theory-based calculations, including hybrid density functionals, and taking the bipyramidal anatase (TiO₂)₈₄ NP as a realistic model. The location of the N dopant is systematically analyzed, including O substitution in the (TiO₂)₈₄ structure and N occupying interstitial regions. Our computational study concludes that interstitial N doping is more favorable than N substituting O atoms and confirms that the presence of N reduces the energy gap. In the N-doped NP, O_vac formation is more favored than in undoped NP but less than in the N-doped bulk, which has important consequences.