MOF-Derived Carbon Networks with Atomically Dispersed\nFe–N_<i>x</i> Sites for Oxygen Reduction\nReaction Catalysis in Acidic Media

Abstract

Proton\nexchange membrane fuel cell (PEMFC) is one of the most promising\ncandidates for electrochemical energy conversion, but the requirement\nof expensive Pt-based catalysts on the cathodes prevents its large-scale\napplication. Herein, we report the preparation of three-dimensional\ncarbon networks with atomically dispersed Fe–N₄ active\nsites (SA-3DNC) for oxygen reduction reaction (ORR) catalysis in the\ncathodes of PEMFCs. Derived from NaCl-assisted pyrolysis, the SA-3DNC\nhas a continuous, micro-macroporous hierarchical morphology which\nis 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\nis 30 mV more positive than that of commercial 20% Pt/C. After 10 000\ncycles of accelerated degradation, the half-wave potential of SA-3DNC\nonly drops 38 mV, compared to 125 mV of the Pt/C. Furthermore, a single\ncell was assembled using the SA-3DNC as the cathodic catalyst, showing\nonly a 20% current drop after a 20-h durability test at 0.5 V. Our\nstudy has demonstrated a facile way to prepare hierarchical, stable,\nand noble-metal-free electrocatalysts with atomically dispersed active\nsites for ORR catalysis in acidic media.