Potential Oscillation Generated by Formic Acid Oxidation in the Presence of Dissolved Oxygen

• Published in: Journal of physical chemistry. C Vol. 112; no. 18; pp. 7186 - 7192
• Main Authors: Kikuchi, Mitsunobu, Miyahara, Sho, Mukouyama, Yoshiharu, Okamoto, Hiroshi
• Format: Journal Article
• Language: English
• Published: American Chemical Society 08.05.2008
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp075940l

The effect of dissolved oxygen (0−1 mM) on the potential oscillation generated by the oxidation of formic acid is investigated with polycrystalline platinum at 315 K in a sulfuric acid solution containing 1 or 0.1 M formic acid. With an increase in the oxygen concentration, an induction period appears with 1 M formic acid at a current density of 4.8 mA/cm2 or greater, while it becomes short with 0.1 M formic acid at most current densities producing oscillation. A fluctuation appears and increases in amplitude and period during the oscillation with 1 M formic acid, and in potential during the induction period with 1 and 0.1 M formic acid. The duration of an entire oscillation decreases, but the maximum current for the appearance of oscillation hardly changes. With 1 M formic acid, the duration of the peak potential increases where small oscillations are observed. The addition of oxygen has two opposite effects on the current:  the anodic current is increased because of oxidation of the adsorbed CO, and the cathodic current is increased because of electrochemical reduction of oxygen. The reasons for the oscillation behavior found upon the addition of dissolved oxygen are discussed on the basis of this fact and the voltammogram results.