Effect of pH and Azide on the Oxygen Reduction Reaction with a Pyrolyzed Fe Phthalocyanine Catalyst

The active site of pyrolyzed Fe/N/C electrocatalysts for the oxygen reduction reaction (ORR) has been a source of debate since the initial discovery that these materials demonstrated activity toward the ORR. Here we utilize carbon-supported iron­(II) phthalocyanine (FePc) that has been pyrolyzed at 800 °C in the absence and presence of azide in acidic, neutral, and basic environments in order to probe the ORR activity and mechanism of pyrolyzed Fe/N/C materials. The presence of azide served to enhance the ORR activity of this material in neutral electrolyte while having no effect in acid or base. Tafel slope differences in addition to the azide enhancement suggest an iron-centered active site for the ORR in pyrolyzed FePc and potentially other Fe/N/C electrocatalysts.