3D-ordered macroporous N-doped carbon encapsulating Fe-N alloy derived from a single-source metal-organic framework for superior oxygen reduction reaction

Fe-N compounds with excellent electrocatalytic oxygen reduction activity are considered to be one of the most promising non-precious metal materials for fuel cells. Fe-N compounds with excellent electrocatalytic oxygen reduction activity are considered to be one of the most promising non-precious metal materials for fuel cells, which focuses on the Fe-N₄ single-atom catalysts and the iron nitride materials (such as Fe₂N and Fe₃N). A hybridized catalyst having a hierarchical porous structure with regular macropores could enable the desired mass transfer efficiency in the catalytic process. In this study, we have constructed a new type of hybrid catalyst having iron and iron-nitrogen alloy nanoparticles (Fe-N austenite, termed as Fe-NA) embedded in the three-dimensional ordered macroporous N-doped carbon (3DOM Fe/Fe-NA@NC) by direct pyrolysis of single-source dicyandiamide-based iron metal-organic frameworks. The as-synthesized composites preserve the hierarchical porous carbon framework with ordered macropores and high specific surface area, incorporating the uniformly dispersed iron/iron-nitrogen austenite nanoparticles. Thereby, the striking architectural configuration embedded with highly active catalytic species delivers a superior oxygen reduction activity with a half-wave potential of 0.88 V and a subsequent superior Zn-air battery performance with high open-circuit voltage and continuous stability as compared to those using a commercial 20% Pt/C catalyst.