Oscillatory behavior in the electrochemical oxidation of formic acid on Pt(100): rotation and temperature effects

We investigated the oscillatory behavior in the kinetics of formic acid electrooxidation on Pt(100) in 1 mM HClO4 solution. We studied the effect of different experimental parameters on the oscillatory behavior, viz. defined HCOOH mass-transport to the electrode surface by using the rotating disk electrode technique, the temperature of the supporting electrolyte, and the nature of anions. We suggest that the interdependence of the reaction steps during HCOOH oxidation, the adsorption of anions and the competition for adsorption sites among the reaction partners and intermediates lead to complex non-linear kinetics. It was evident that once the individual reactions in the dual path mechanism reach steady state the oscillations vanish. These conditions can be reached either by enhanced formic acid reaction rates induced by electrode rotation or by increased temperature. Under specific conditions of anion and formic acid concentration, relaxational oscillations can be transformed into mixed-mode oscillations.