Single atom Fe-based catalyst derived from hierarchical (Fe,N)-ZIF-8/CNFs for high-efficient ORR activity

The development of high-efficiency, stable, and low-cost Fe-N-C electrocatalysts for the oxygen reduction reaction (ORR) has attracted considerable attention. Herein, a stable atomically dispersed Fe-Nx-based catalyst was synthesized from a hierarchical structure involving carbon nanofiber (CNF)-supported zeolitic-imidazolate-framework-8 (ZIF-8) encapsulated Fe-Phen complex ((Fe,N)-ZIF-8/CNFs). The Fe-Nx-CNFs obtained from the pyrolysis of (Fe,N)-ZIF-8/CNFs showed a good hierarchical multi-layer structure. The natural network structure of the carbon nanofibers serves as a matrix to uniformly distribute the ZIF-8 particles, and the Fe-Nx sites derived from the Fe-Phen complex were uniformly distributed in ZIF-8 particles. It exhibits excellent ORR performance with a high half-wave potential of 0.875 V (vs. RHE), which was 55 mV higher than that of the commercial Pt/C catalyst. In addition, density functional theory (DFT) calculations on the catalyst further revealed the origin of the ORR activity via a 4e(-) pathway from the precise local coordination of FeN4 sites.