Investigation of the mechanism of the electrochemical oxidation of formic acid at a gold electrode in sulfuric acid solution

The oxidation of formic acid at the Au electrode in sulfuric acid solution was investigated using a programmed potential step procedure. The j-t curve of the direct reactive oxidation of formic acid suggested a two-stage mechanism of the electrode reaction. The oxidation current density peak on the chronoamperometric plot corresponded to the formation of a steady adsorptive layer of COOHads through adsorption of HCOOH and the first electron transfer, while the steady current density corresponded to the further oxidation of the adsorptive layer of COOHads formed, A data fitting program was developed for extracting kinetic parameters from the j to t transient experimental data. The adsorption rate constants (k(a)) for formic acid, the reaction rate constants (k(2)) and the transfer coefficient (beta) for the further oxidation of COOHads were obtained at various potentials. These results confirmed that the further oxidation of COOHads was the rate-limiting step after the adsorption balance of COOHads was achieved, and before that, the adsorption of formic acid was the rate-limiting step. (C) 2001 Elsevier Science B.V. All rights reserved.