Increases in reaction rates and improvement of current-potential characteristics in the electrochemical oxidation of formic acid

In current-control experiments, perturbing an aqueous solution containing 0 .10 M formic acid and 0.50 M HClO4 by including a small amount of HBF4 caus es more than a 60% increase in the value of the applied current for which l ow-valued stationary potentials remain stable. The current increases by mor e than 50% at relevant potential values in potential-control experiments. C urrent-potential characteristics inferior to those of the HCOOH + HClO4 sol ution are obtained with other solutions made by adding small amounts of a s trong acid or salt. Properties that exist among the anions present in the l atter solutions are possessed by BF4-. Nonlinear behavior exhibited by form ic acid oxidation is changed drastically by the presence of a small amount of any one of the anions studied. These results and other arguments support the hypothesis that HBF4 enhances current-potential characteristics by cau sing the formation of surface anion complexes possessing OH components at l ow potentials. (C) 2001 Elsevier Science B.V. All rights reserved.