Zeta potential and photocatalytic activity of nitrogen doped TiO2 thin films

Nitrogen doped TiO2 films were fabricated by annealing anatase TiO2 films in gaseous NH3. Nitrogen atoms in these films were substitutionaly introduced into oxygen sites of TiO2 lattice. We have evaluated the zeta potential of these films and have found that it became negative with the amount of nitrogen doping. The photocatalytic decomposition of gaseous 2-propanol was examined under light-limited conditions, and the quantum yield (QY) was estimated while illuminating with ultraviolet (UV) and visible light (VIS). The QY values for the nitrogen doped TiO2 film were 15.4% (UV) and 0.41% (VIS), whereas those for the pure TiO2 film were 18.4% (UV) and 0% (VIS). In addition, the photocatalytic decomposition of ethylamine ions (CH3CH2NH3+) was evaluated in an aqueous solution under UV illumination in a light-rich condition. Consequently, the decomposition rate of the nitrogen doped TiO2 for aqueous ethylamine ions was higher than that of the pure TiO2 because the surface of the nitrogen doped TiO2 film was negatively charged and cationic ethylamine ions were efficiently adsorbed on its surface. The surface structure and the band structure of the nitrogen doped TiO2 are discussed in this paper.