A Rational Synthetic Approach to Highly Active Fe-N-C Catalyst for Efficient Electrochemical Oxygen Reduction

Abstract

Single atoms of iron coordinated to nitrogen embedded in carbon support (Fe-N-C) are the most active platinum group metal free catalysts for oxygen reduction reaction (ORR) in renewable energy devices. The Fe-N-C catalysts, customarily derived from Fe-doped zeolitic imidazole frameworks suffer from limited activity due to restricted utilization of the active sites which are buried deep inside the carbon matrix. Herein, we report a unique but facile design approach based on the interplay between oxidation state of Fe in the precursor and modulation of synthetic parameters to regulate the particle size, surface area and Fe-doping towards increased accessible ORR active sites. The synthesized Fe-N-C catalyst demonstrates remarkably high ORR activity in 0.1 M KOH with onset and half-wave potential of 0.988V and 0.903V vs RHE, excellent 4e^- selectivity and durability. Our work paves the way for a new discussion in understanding the role of fundamental parameters that affect material’s properties through unique design strategy.