EFFECTS OF ANIONS LEADING TO INCREASES IN STEADY STATE EFFICIENCY AND REACTION RATES IN THE ELECTROCHEMICAL OXIDATION OF FORMIC ACID

摘要

Effects of anion adsorption on the oxidation of formic acid at Pd and Pt are studied. Evidence supports the conclusion that the role of anions is more than simply blocking reactive surface sites. In current-control experiments, the composition of the supporting electrolyte and the ratio of the supporting electrolyte concentration to that of the solute were varied. Unlike previous potential-control experiments, which produced quantitative results, varying the type and composition of the electrolyte caused drastic changes in the behavior exhibited by the oxidation of formic acid. Several experiments established trends that are opposite to those that would be predicted if the only effect of anions was to block surface sites. Several experiments were conducted in which the changes in behavior were examined that arose from perturbing an HCOOH + HClO_4 solution by adding a strong acid or salt. Almost all current-potential characteristics were inferior to those of the unperturbed solution. However, in current-control experiments, perturbing the solution by including a small amount of HBF_4 caused more than a 60% increase in the value of the applied current for which low valued stationary potentials remain stable. In potential control experiments, the current increased by more than 50% within a certain potential range.