Polypyrrole derived carbon nanotube aerogel based single-site Fe-N-C catalyst with superior ORR activity and durability

Single-atom catalysts maximize atomic utilization efficiency while providing tunable active sites, making them promising candidates for replacing expensive noble metals in electrochemical reactions. However, isolated metal atoms tend to aggregate irreversibly due to high surface energy, deteriorating both activity and durability. Herein, we report a single-site Fe-N-C oxygen reduction reaction (ORR) catalyst synthesized by pyrolyzing an iron-loaded polypyrrole aerogel precursor. The resultant Fe-N-C catalyst comprises crosslinked nitrogen-doped carbon nanotubes with high specific surface area and abundant mesopores. Compared to commercial Pt/C, it demonstrates remarkable improvements in half-wave potential (0.81 V vs 0.84 V) and limiting current density (4.31 mA cm−2 vs 4.8 mA cm−2) for ORR. Stability and methanol tolerance tests further verify excellent durability under alkaline conditions. Crucially, by applying this Fe-N-C catalyst in anion exchange membrane fuel cells, outstanding peak power density of 150 mW cm−2 is achieved, outperforming commercial Pt/C cathodes (127 mW cm−2). Our single-site catalyst provides a promising strategy to develop durable and active non-precious metal ORR electrocatalysts through rational aerogel precursor design and pyrolysis.