Photochemical Activity of Nitrogen-Doped Rutile TiO₂(110) in Visible Light

Abstract

TiO 2 (110) single crystals, doped with nitrogen via an NH 3 treatment at 870 K, have been found to exhibit photoactivity at photon energies down to 2.4 eV, which is 0.6 eV below the band-gap energy for rutile TiO 2 . The active dopant state of the interstitial nitrogen that is responsible for this effect exhibits an N (1s) binding energy of 399.6 eV and is due to a form of nitrogen that is probably bound to hydrogen, which differs from the substitutional nitride state with an N (1s) binding energy of 396.7 eV. Optical absorption measurements also show enhanced absorption down to 2.4 eV for the NH 3 -treated TiO 2 (110). A co-doping effect between nitrogen and hydrogen is postulated to be responsible for the enhanced photoactivity of nitrogen-doped TiO 2 materials in the range of visible light.