Nitrogen doping-induced changes in the electronic properties, defect formation, and surface structure of rutile(110) and anatase(101) single crystals were investigated. No band-gap narrowing was observed, but N doping introduced localized N 2p states into the band gap, just above the valence band. The N was present in a N(III) valence state, which facilitated the formation of O vacancies and Ti 3d band gap states at elevated temperatures. The increased O vacancy formation triggered 1×2 reconstruction of the rutile (110) surface. This thermal instability could degrade the catalyst.

Influence of Nitrogen Doping on the Defect Formation and Surface Properties of TiO2 Rutile and Anatase. M.Batzill, E.H.Morales, U.Diebold: Physical Review Letters, 2006, 96[2], 026103 (3pp)