Methods to Improve Electrochemical Reversibility at Carbon Electrodes

Carbon electrodes are frequently used for electroanalytical studies of oxidizable compounds. However, for many compounds, heterogeneous charge‐transfer rates are very slow at carbon electrodes, leading to ill‐defined voltammograms. Ascorbic acid (vitamin C) is perhaps one of the best examples of such phenomena, with a peak potential that is approximately 350 mV more positive at most carbon surfaces than at mercury electrodes. Ferricyanide also exhibits voltammetry at carbon electrodes that is less reversible than at noble metal electrodes. Various electrode surface treatments have been employed to accelerate the rates of ascorbate and ferricyanide electrolysis. Pretreatment of carbon fiber electrodes with a high current density results in a significant shift of the voltammetric waves for both compounds to potentials where they are more easily electrolyzed. Similar results are obtained with glassy carbon surfaces that have been heated at 500°C under reduced pressure. An alternate method to increase reversibility is the judicious use of polishing procedures. Thus, it appears that the surface properties of carbon electrodes can have profound effects on the observed voltammetry.