Efficient yolk-shelled Fe-N-C oxygen reduction electrocatalyst via N-rich molecular-guided pyrolysis.

Abstract

Fe-N-C catalysts with highly dispersed metal active centers were developed as promising non-precious metal materials for acidic oxygen reduction reaction (ORR) electrocatalysis. However, such kind of novel catalysts still suffer from major challenges in the manipulation of dispersion, utilization, and stability of the Fe-based metal centers. Herein, a N-rich molecular dual-guided pyrolysis strategy was proposed to develop an efficient yolk-shelled Fe-N-C ORR electrocatalyst. A unique yolk-shelled nanostructure with a relatively ordered shell and disordered yolk of a carbon skeleton was controllably constructed via this guided-pyrolysis route from the precursor of Fe-doped zeolitic imidazolate framework-8 (Fe-ZIF-8). Moreover, the atomic-level dispersion of Fe element in the carbon skeleton could be achieved via the dual guidance from phenanthroline and melamine molecules. The optimized Fe-N-C catalyst demonstrated a half-wave potential of 0.78 V vs. RHE in acid media, close to commercial 30% Pt/C, along with a small negative shift of 19 mV after an accelerated durability test. These enhanced electrocatalytic properties could be attributed to the preferred transformation of the Fe precursors to atomically dispersed Fe-Nx active configurations, as well as the enhanced three-phased interfacial reaction kinetics.