Hyeonseok Yoo

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 (≈0.12 wt %) into 25 μm 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.

Effects of Metal Anion Complexes in Electrolyte on the Properties of Anodic Oxide Films on ADC12 Al Alloy

The anodization of ADC12 aluminum alloy was investigated in the metal anionic acid media. Anodic oxide films containing foreign elements were formed on ADC12 Al alloy by anodization in the anion complex solution. Furthermore, the rough surface and cracks were considerably smoothened by the deposit of metal anions. When the size of metal anion was small, relatively large amount of metal anions was loaded in anodic films. Existence of MoO₃, TiO₂ and MgO was confirmed by XPS. According to the results of Tafel analysis, Mo oxide represented the most noble anti-corrosion potential due to MoS2 formation. Corrosion current densities were generally higher than that of pristine anodic oxide without anion complexes.