KINETICS OF OXYGEN REDUCTION ON CARBON MATERIALS IN ALKALINE-SOLUTION

Oxygen reduction in alkaline solution on a wide range of carbon blacks, active carbons, and graphites has been studied using the ultra thin electrode technique. Results were obtained as a function of pH and KOH concentration, oxygen partial pressure, and temperature. Under all conditions, the pH dependence of the reaction (vs nhe) at constant cd is zero, as pH (or KOH concentration) increases. In concentrated alkali, a change in mechanism is noted. The pH region for this change increases as BET area of the carbon increases. A mechanism is suggested to account for these observations, which do not involve a reversible O2/O2H- couple. For carbons exhibiting the second (∼2RT/3F Tafel slope) mechanism in 6 N KOH, activity is proportional to available surface area. © 1979.