Electrochemical oxidation of formic acid at carbon supported Pt coated rotating disk electrodes

Resumo

The effect of electrode rotation on the oxidation of formic acid in aqueous sulphuric acid has been investigated at a glassy carbon electrode coated with a carbon supported Pt catalyst. Substantial mass transport effects were observed in cyclic voltammetry, steady-state measurements at constant potential, and chronoamperometry. However, a purely mass transport limited current was not observed under any conditions because of a decrease in the kinetic current at high potentials due to Pt oxide formation. Steady-state measurements, and currents from the cathodic scans in cyclic voltammetry, gave linear Koutecky–Levich plots with slopes in agreement with the literature diffusion coefficient. However, non-linearity and inaccurate slopes were observed for anodic scans and chronoamperometry. This has been shown to be due to small increases in the kinetic current with increasing rotation rate. Accurate kinetic currents can be obtained by applying the Koutecky–Levich equation at each rotation rate and use of the known mass transport limited current.