Low overpotential nanocrystalline Ti-Fe-Ru-O cathodes for the production of sodium chlorate

Non-stoichiometric metal-oxygen nanocrystalline alloys have been produced by high energy ball milling various mixtures of metallic and oxide powders. The system Ti-Fe-Ru-O has been explored to some extent. Structural evolution on milling has been followed by x-ray diffraction. After milling, the powder is cold pressed in the form of a circular disc to be used as cathode for the electrochemical synthesis of sodium chlorate. The electrochemical properties (overpotential, chemical inertness and long term stability in the electrolyte) were investigated as a function of the alloy composition. We have measured, for some nanocrystalline alloys, an overpotential 300 mV lower than that of the steel cathodes (eta(250 mA/cm)2 approximate to 900-1000 mV). Steel is the commonly used cathode in this industry. Long term stability has been tested for over 1000 hours on nanocrystalline Ti32Fe20Ru16O32 without showing any visible degradation. This material is also chemically inert with respect to the decomposition of the hypochlorite.