Core-shell MOF-derived Fe3C-Co-NC as high-performance ORR/OER bifunctional catalyst

Abstract

Metal–organic framework (MOF)-derived carbon materials have emerged as important candidates in the field of catalysis because of their simple synthesis, easy construction, good conductivity, and high catalytic activity. Fe3C nanoparticles prepared from MOFs facilitate the catalytic activity of adjacent single atoms and exhibit powerful catalytic properties. In this work, a composite structured catalyst with Fe3C, Co nanoparticles, and M-Nx single atoms (M = Co, Fe) was synthesized (denoted as Fe3C-Co-NC) by constructing Fe-doped bilayer zeolitic imidazolate frameworks (ZIFs) with a core–shell structure, which were used as bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The Fe3C-Co-NC catalyst exhibits superior half-wave potential (E1/2 = 0.89 V) and overpotential (Ej=10 = 1.67 V) and outperforms the commercial Pt/C and RuO2. This result can be attributed to the high specific surface area, hierarchical pore structure, and high graphitization degree of the Fe3C-Co-NC catalyst, especially the synergistic effect between Fe3C and adjacent single-atom active sites. Specifically, the Zn–air battery assembled using the Fe3C-Co-NC catalyst displays high peak power density (203 mW cm−2) and specific capacity (815 mAh g−1) without degradation after charge/discharge cycles for 57 h. Therefore, this work offers important insights into the design and research of high-performance ORR/OER bifunctional catalysts.