VOLTAMMETRIC STUDIES OF GLASSY-CARBON ELECTRODES ACTIVATED IN AIR AND STEAM

Polished glassy carbon electrodes were activated in either air at 400-degrees-800-degrees-C or steam at 790-degrees-980-degrees-C. Square wave voltammetry of air-activated electrodes in McIlvaine buffer revealed the presence of a significant surface redox couple. Nernst plots of the peak potential vs. pH gave an average slope of -75 +/- 2 mV. The data are consistent with the presence of a quinone-hydroquinone-type couple. Heat treatment of the electrodes in the presence of gases increased the electron transfer rate of the Fe(CN)6(3-/4-) couple, regardless of whether steam, air, or argon was used. Large increases in surface area were noted under appropriate temperature conditions for both air and steam treatments. Following steam treatment, negligible surface redox activity was detected on the electrodes. In addition to the redox behavior. there were also substantial differences between the physical appearances of air- and steam-activated surfaces. Activated glassy carbon surfaces may be useful models for the behavior of activated carbon itself.