(419g) An Electrochemical Impedance Study of Formic Acid Electrooxidation On Palladium

Formic acid has drawn increased interest for use in direct liquid fuel cells as well as serving as a model compound for the electro oxidation of other small organic molecules.  In this work, electrochemical impedance spectroscopy is utilized to investigate the electro oxidation of formic acid on a smooth polycrystalline palladium electrode in a sulfuric acid solution. Palladium based catalysts have shown significant promise in direct formic acid fuel cells.  While there is broad agreement about the basic aspects of the mechanism of formic acid electrooxidation, there remains some disagreement on some specific aspects, in particular the nature of some of the intermediates formed.  Equivalent circuits are derived from the various proposed mechanisms and the quality of the fit of these to the impedance data is examined.  Key kinetic parameters have also been extracted from the impedance data.  The oscillatory behavior of the electro oxidation reaction is also examined and the mechanism compared to that on a polycrystalline platinum electrode.