(254d) Impedance Spectroscopy Study of the Electrooxidation of Formic Acid On Platinum

Formic acid electro-oxidation is among the most widely studied molecules in electrochemistry. In recent years, it has received renewed interest due to the potential shown by direct formic acid fuel cells for portable power generations. It is generally accepted that formic acid electro-oxidation occurs via two reaction pathways: a direct pathway where CO2 is produced without an intermediate step and an indirect pathway where a CO reaction intermediate is formed. Despite the large number of studies using electrochemical or spectroscopic techniques, many details of the mechanism remain unclear. In this work, we utilize electrochemical impedance spectroscopy to provide new insights into the mechanism of the electro-oxidation of formic acid on a smooth polycrystalline platinum electrode in sulfuric acid. An array of impedance spectra were collected at and around the potentials of the various reaction, adsorption, and desorption steps and the results compared with those from cyclic voltammetry measurements. By fitting the impedance data to appropriate reaction models, information relating to the reaction kinetics, absorbed intermediates, and the mechanism of formic acid electro-oxidation are revealed.