Iron atom-cluster interactions increase activity and improve durability in Fe-N-C fuel cells

Simultaneously increasing the activity and stability of the single-atom active sites of M-N-C catalysts is critical but remains a great challenge. Here, we report an Fe-N-C catalyst with nitrogen-coordinated iron clusters and closely surrounding Fe-N-4 active sites for oxygen reduction reaction in acidic fuel cells. A strong electronic interaction is built between iron clusters and satellite Fe-N-4 due to unblocked electron transfer pathways and very short interacting distances. The iron clusters optimize the adsorption strength of oxygen reduction intermediates on Fe-N-4 and also shorten the bond amplitude of Fe-N-4 with incoherent vibrations. As a result, both the activity and stability of Fe-N-4 sites are increased by about 60% in terms of turnover frequency and demetalation resistance. This work shows the great potential of strong electronic interactions between multiphase metal species for improvements of single-atom catalysts. It is challenging to break the activity-stability trade-off in Fe-N-C fuel cell catalysts. Here, the authors show that interactions between iron atoms and clusters accelerate reaction kinetics and suppress demetalation to improve fuel cell stability.