Application of surface science techniques in the study of environmental photocatalysis: nitrogen-doped TiO₂

In order to understand the origin of visible-light photocatalysis by nitrogen-doped titania, titania (anatase) films whose composition can be varied in a controlled way have been grown in situ and subsequently characterized by XPS, UPS, and ex situ AFM. Two very different in situ methods for nitrogen-doping were used, N⁺ implantation and nitride oxidation, and the chemical identity and depth distributions of the resulting chemical species were established. It is found that N⁺ implantation results in extensive reduction of the titania, re-oxidation with O₂ establishing an essentially oxidized surface. Both methods of preparation result in the nitrogen being located beneath the surface. These results have significant implications for our understanding for the origin of visible light activity of nitrogen-doped catalysts. In particular, they indicate that earlier interpretations may be oversimplified or even incorrect. To cite this article: A. Orlov et al., C.R. Chimie 9 (2006).