Switching of Electron Transport Direction from the Long Axis to Short Axis in a Radial SnO(Head)-Rutile TiO Nanorod(Tail) Heteromesocrystal Photocatalyst.

Heteroepitaxial growth of rutile TiO nanorods from SnO seeds yielded radial heteromesocrystals consisting of SnO(head) and rutile TiO nanorod(tail) with the SnO(head) oriented toward the center (TiO-NR//SnO HEMCs). Iron oxide clusters were formed on the surface by the chemisorption-calcination technique. The FeO-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-TiO-NR//SnO HEMC, electrochemical measurements were performed for the rutile TiO-NR array formed on a fluorine-doped tin oxide (SnO:F) electrode. The results showed that the FeO clusters possess electrocatalytic activity for a multielectron oxygen reduction reaction, and the high photocurrent of the electrode is remarkably reduced by the FeO-surface modification. Consequently, the striking photocatalytic activity of FeO/TiO-NR//SnO HEMCs was ascribable to the switching of the electron transport direction necessary for the charge separation from the long axis of the TiO NR to the short axis.