Switching of Electron Transport Direction from the Long Axis to Short Axis in a Radial SnO₂(Head)–Rutile TiO₂ Nanorod(Tail) Heteromesocrystal Photocatalyst

Heteroepitaxial growth of rutile TiO₂ nanorods from SnO₂ seeds yielded radial heteromesocrystals consisting of SnO₂(head) and rutile TiO₂ nanorod­(tail) with the SnO₂(head) oriented toward the center (TiO₂-NR//SnO₂ HEMCs). Iron oxide clusters were formed on the surface by the chemisorption–calcination technique. The FeO_x-surface modification gives rise to drastic increases in the photocatalytic activity for aerobic oxidation of 2-naphthol under irradiation of UV and visible light. As a 2D-model for 3D-TiO₂-NR//SnO₂ HEMC, electrochemical measurements were performed for the rutile TiO₂-NR array formed on a fluorine-doped tin oxide (SnO₂:F) electrode. The results showed that the FeO_x clusters possess electrocatalytic activity for a multielectron oxygen reduction reaction, and the high photocurrent of the electrode is remarkably reduced by the FeO_x-surface modification. Consequently, the striking photocatalytic activity of FeO_x/TiO₂-NR//SnO₂ HEMCs was ascribable to the switching of the electron transport direction necessary for the charge separation from the long axis of the TiO₂ NR to the short axis.