Abstract
We describe a study of the oxygen reduction kinetics at the Pt/recast Nafion® interface employing a minicell based on a filmed microelectrode. The experimental conditions are identical to those in polymer‐electrolyte fuel cells in that the recast ionomer electrolyte is exposed only to water vapor. We find that the interfacial rate of oxygen reduction near 0.9 V is similar for the Pt/recast ionomer interface and for Pt immersed in dilute aqueous acid solutions. A significant loss of oxygen reduction activity occurs when the recast ionomer electrolyte loses water. We discuss a possible evaluation of catalyst utilization in polymer electrolyte fuel cells.