Highly Active Oxygen Reduction Electrocatalysts Derived from an Iron-Porphyrin Framework

Abstract

The high cost of noble metals is a barrier to widespread commercialization of polymer electrolyte membrane fuel cells. Platinum-group-metal-free catalysts are a promising low-cost alternative for catalyzing the oxygen reduction reaction (ORR). Herein, we report a high activity Fe-N-C cathode catalyst derived from a Fe-porphyrinic framework prepared using low-cost precursors and facile one pot synthesis followed by a single heat treatment. The final product has atomically dispersed iron in proximity to nitrogen groups that share transition metal characteristics, as described by electron energy loss spectrometry and x-ray absorption near edge structure results. Electrochemical studies on a rotating ring-disk electrode indicate a four-electron transfer mechanism for the ORR. Membrane electrode assembly testing of the Fe-porphyrin-derived cathode catalyst shows a high kinetic current density of 22 mA cm^{−2} at 0.9 V in H_{2}-O_{2} fuel cells.