title: Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.
abstract: The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts.
authors: EcoTopia Science Institute, Nagoya University, Nagoya 464-8603, Japan. Electronic address: tyoshida@nucl.nagoya-u.ac.jp.
authors: Tomoko
authors: T
authors: Yoshida
authors: Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors: Satoshi
authors: S
authors: Niimi
authors: Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors: Muneaki
authors: M
authors: Yamamoto
authors: Aichi Synchrotron Radiation Center, 250-3, Minamiyamaguchi-cho, Seto 489-0965, Japan.
authors: Toyokazu
authors: T
authors: Nomoto
authors: EcoTopia Science Institute, Nagoya University, Nagoya 464-8603, Japan.
authors: Shinya
authors: S
authors: Yagi
keywords: Photocatalyst; TiO(2); XAFS; XPS