MOF-Derived Carbon Networks with Atomically Dispersed Fe-N_x Sites for Oxygen Reduction Reaction Catalysis in Acidic Media

Proton exchange membrane fuel cell (PEMFC) is one of the most promising candidates for electrochemical energy conversion, but the requirement of expensive Pt-based catalysts on the cathodes prevents its large-scale application. Herein, we report the preparation of three-dimensional carbon networks with atomically dispersed Fe-N₄ active sites (SA-3DNC) for oxygen reduction reaction (ORR) catalysis in the cathodes of PEMFCs. Derived from NaCl-assisted pyrolysis, the SA-3DNC has a continuous, micro-macroporous hierarchical morphology which is endowed by the modulator effect of the molten salt. In 0.1 M HClO₄, the SA-3DNC has a 0.906 V onset potential for ORR, which is 30 mV more positive than that of commercial 20% Pt/C. After 10 »000 cycles of accelerated degradation, the half-wave potential of SA-3DNC only drops 38 mV, compared to 125 mV of the Pt/C. Furthermore, a single cell was assembled using the SA-3DNC as the cathodic catalyst, showing only a 20% current drop after a 20-h durability test at 0.5 V. Our study has demonstrated a facile way to prepare hierarchical, stable, and noble-metal-free electrocatalysts with atomically dispersed active sites for ORR catalysis in acidic media.