Development of a visible-light-responsive rutile rod by site-selective modification of iron(III) ion on {1 1 1} exposed crystal faces

{1 1 1} exposed crystal faces of shape-controlled rutile titanium(IV) oxide (TiO2) were site-selectively modified with trivalent iron(III) (Fe3+) ions by utilizing adsorption property of iron(III)/iron(II) (Fe3+/Fe2+) ions. The rutile TiO2 with site-selective modification of Fe3+ ions showed high photocatalytic activity under visible-light irradiation as a result of separation of redox sites, i.e., oxidation and reduction proceed over Fe3+ ions on {1 1 1} faces and the bare TiO2 surface on {1 1 0} faces, respectively. Double-beam photoacoustic spectroscopic analyses suggest that the high activity of TiO2 with site-selective modification of Fe3+ ions is attributed to not efficient electron injection from Fe3+ ions but efficient reduction by injected electrons on {1 1 0} faces.