Electrochemical Oxidation Of Oxalic Acid Research Articles

Electrocatalytic oxidation of oxalic acid at electrodes coated with polymeric metallophthalocyanines

The overpotential normally associated with the electrochemical oxidation of oxalic acid in aqueous solution is greatly reduced at glassy carbon surfaces modified with polymeric metallophthalocyanine films. The cobalt derivative is particularly active, displaying a peak potential ~ 750 mV less positive than that obtained at a bare electrode. The electrocatalytic process appears to involve initial Co II → Co III oxidation, and the mechanistic details have been examined using cyclic voltammetry and rotating disk electrochemical methods. The overall reaction is quite rapid, and Levich plots obtained at coated electrodes show only slight deviations from linearity, even at high rotation rates. The observed catalytic current depends linearly on oxalic acid concentration and varies only slightly with film thickness, suggesting that internal charge transport is not rate-limiting under these conditions. The data indicate that the electrocatalytic oxidation of oxalic acid at polymeric cobalt phthalocyanine-coated electrodes belongs to the SR kinetic regime.

The mechanism of the electrochemical oxidation of oxalic acid

Oxalic acid oxidation on platinized platinum has been studied at 80°C in solutions of H2 SO4, Na2SO4 and NaOH. Reaction rates were measured as a function of potential, pH and concentration of oxalic acid. Coulombic efficiency was determined by measurements of CO2 production. Empiricallyi = kcH2C2O40·35cH+−0·55 exp (FV/RT).Coulombic efficiency of oxidation to CO2 is ca 100%. No oxidation occurs in alkaline solutions.The results are interpreted in terms of a mechanism having the following characteristics.Undissociated acid is the reacting species. Oxidation occurs under Temkin conditions. Both electrons are supplied by the organic species. The second charge transfer is the rate-determining step.