OXYGEN REDUCTION ON A ROTATING PT DISC ELECTRODE IN FORMIC ACID-CONTAINING SOLUTIONS

The effect of HCOOH on the reduction of oxygen in sulfuric acid solution is investigated by using a rotating Pt disc electrode. The reduction of oxygen and the oxidation of HCOOH during the negative potential sweep interfere with each other. When the concentration of HCOOH is less than 0.01 mol dm(-3), the reduction of oxygen is not affected at higher potentials. However, the oxidation of HCOOH is completely suppressed, probably owing to the consumption of adsorbed HCOOH fragments through reaction with oxygen. The results show that the electrode activity for the reduction of oxygen becomes unacceptable when the HCOOH concentration is higher than 0.1 mol dm(-3), since the potential for the onset of the reduction of oxygen shifts in a very negative direction. It is suggested that the decrease in the activity of the reduction of oxygen is due to the adsorption of HCOOH fragments on the electrode suface. However, there is no evidence that the mechanism of the reduction of oxygen is altered by the adsorption of HCOOH.