Optical properties and structure of the TiN-nitrogen-doped TiO2 nanocomposite

As one of the most versatile photocatalysts, TiO2 is suitable for numerous environmental and energy related applications, however its efficiency is limited by its wide band gap. Doping with anions such as nitrogen has been successful in extending the TiO2 solar absorption into the visible spectrum, although the exact nature and optimal level of N doping are still debated. Present study shows that excessive and mostly substitutional N doping can result in an in situ formation of nanocomposite structure consisting of TiN nano-crystals embedded in the N-doped anatase TiO2, in addition to effectively doping TiO2 by adding electronic states at the valence band edge thereby narrowing its band gap, as reported before. The metal-semiconductor interfaces in the thin film induce local band bending in the N-doped TiO2 phase and this may assist in separating the photogenerated charge carriers. The possible interplay between the two phases is discussed. Very low levels of N doping were found not to have any impact on the band gap of TiO2. (C) 2014 Elsevier B.V. All rights reserved.