Template-free modulation of MOF-derived atomically dispersed Fe-N-C catalyst for enhanced oxygen reduction reaction and durability in acidic medium

This study reports the successful synthesis of a noble metal-free metal-organic framework-derived Fe-N-C catalyst with promising oxygen reduction reaction (ORR) activity and durability in acidic medium via a template-free approach. The modulation of imidazole and iron precursors' composition of Fe-ZIF-8 has led to the formation of a unique graphitic shell-like structure decorated on dodecahedron-shaped particles with uniform bimodal pores and ultralow Fe loading of 0.46 at.% atomically dispersed over the surface. This unique combination resulted in significantly enhanced ORR kinetics compared to other Fe-N-C catalysts. The catalyst demonstrated a high onset potential of 0.92 V vs RHE and the ability to retain 95% current density after 50,000 s chronoamperometry analysis with no significant half-wave potential loss over 5000 load cycles accelerated durability test. Furthermore, the ten-month-aged sample maintained its onset potential with minimal half-wave potential loss over 20,000 load cycles. This work revealed that the ORR kinetic is improved by tuning the iron content to an appropriate atomic composition, with similar nitrogen-bonding configurations on the Fe-N-C catalysts, proving that FeNx is the key active site through an experimental approach. This work underscores the importance of precursor optimization in developing high-performance Fe-N-C catalysts without the need for additional materials. © 2024 Elsevier B.V.