Visible light sensitive photocatalysts are required to use solar energy effectively and for indoor applications. Since Asahi et al. reported that nitrogen-doped TiO₂ showed photocatalytic activity under visible light irradiation, various types of TiO₂ doped wth anions, such as sulfur, carbon, iodine etc. have been widely studied. All of them are sensitive to visible light due to an isolated narrow composed of anion p orbital above valence band.[1] In contrast, there are few reports on the sensitization of TiO₂ to visible light by controlling electronic structure of the conduction band because its bottom is very close to the potential of one electron oxygen reduction.
However, Ohtani et al. reported that platinum-deposited WO₃ showed efficient activity under visible light irradiation although the potential of the conduction band bottom of WO₃ is more positive than that of one electron oxygen reduction.[2] Platinum is an efficient oxygen reduction catalyst in that it proceeds through two or four electron transfer process. So, we can expect the generation of visible light sensitivity by utilising multi-electron oxygen reduction process, even if the bottom of TiO₂ conduction band shifts to more positive position in order to absorb visible light.
In the present study, we confirmed that platinum-deposited Ce-doped TiO₂ under visible light irradiation could effectively decompose gaseous 2-propanol into acetone and CO₂. The details will be introduced at the conference.

[1] For example, R. Asahi et al., Science 2001, 293, 269 [2]Ohtani et al., photocatalysis 2007, 23, 58