Fabrication and Characterization of TiO₂ Nanotube Array for Seawater Splitting Electrode Prepared by Anodization

Among the technologies for hydrogen production, water splitting is a technology that attracts much attention that doesn't cause carbon emissions. But there is a limitation in using highly purified fresh water for hydrogen production through water splitting. Only 2.5 vol% of the water on Earth is fresh water and the other is seawater, and freshwater has many uses, so applied research for the use of seawater is necessary for the dissemination of water-splitting technology. To splitting seawater, the oxygen evolution reaction (OER) electrode requires some unique properties such as high catalytic activity for seawater and chlorine corrosion resistance. To improve these properties, methods for the fabrication of various nanostructures have been suggested and among them, anodization is a method that can be growing aligned nanotube arrays on the surface of a TiO₂ plate. In this study, the TiO₂ OER electrode was fabricated by anodizing to improve catalytic activity and resistance to chlorine corrosion. Morphological and electrochemical properties of TiO₂ OER electrode were characterized using field emission scanning electron microscopes, X-ray diffraction, cyclic voltammetry, and Ultraviolet-visible spectroscopy. Among the anodized electrodes, the sample fabricated in electrolyte using NH₄F-H₂O-C₃H₈O₂ was shown the most hydrogen evolution, and the best resistance to chlorine corrosion was measured for the sample in which the H₂SO₄ electrolyte was used. The average pore diameter of the nanotubes was measured to be below 114 nm using FE-SEM image analysis, and the layer thickness was observed to be more than 10μm.