Influence of metal ions on the photocatalytic activity: Selective oxidation of benzyl alcohol on iron (III) ion-modified TiO2 using visible light

Photocatalytic activity of the surface-modified TiO2 loaded with several metal ions such as iron, silver, cerium, platinum, or copper for the oxidation of benzyl alcohol were investigated under visible-light irradiation. Among the metal ion-modified TiO2, the iron (III) ion-modified TiO2 was found to exhibit the highest photocatalytic performance with the selectivity (>99%) to benzaldehyde. From the analysis of absorption spectra, apparent quantum yields and DFT calculations, the contribution of the Fe3+ ions on the TiO2 to the photocatalytic reaction was demonstrated. It was confirmed that a remarkable enhancement of the photocatalytic activity is attributed to a synergetic effect, i.e., the efficient electronic transitions from the energy levels constructed by the O 2p orbitals of the alcoholate species hybridized with the occupied Fe 3d orbitals to the conduction band of the TiO2, as well as subsequent electron transfers to the unoccupied Fe 3d orbitals as the acceptor levels followed by O2 reduction.