Ruthenium Oxide-Doped TiO2 Nanotubes by Single-Step Anodization for Water-Oxidation Applications

Single-step anodization in NH4F-based ethylene glycol electrolyte containing KRuO4 and H2O led to the production of high-aspect-ratio TiO2 nanotubes (NTs) with a doping of ruthenium oxide. These NTs were successfully used as electrodes for water oxidation in KOH. This method offers homogenous incor poration of a small amount of ruthenium oxide (approximate to 0.12wt%) into 25m TiO2 nanotubes without the need for complicated facilities or steps. The addition of H2O into electrolytes is a key step for the stable adhesion of long-length TiO2 NT films on a substrate. The tips of the TiO2 nanotubes prepared by this novel method are not easily dissolved by electrolyte because the walls of the nanotubes are thickened by a factor of more than two in response to the addition of KRuO4 and H2O. The longest nanotubular TiO2 with a doping of ruthenium oxide and no wall dissolution shows the largest current density in the oxygen-evolution reaction.