Metal-organic framework-derived mesoporous carbon nanoframes embedded with atomically dispersed Fe-Nx active sites for efficient bifunctional oxygen and carbon dioxide electroreduction

Metal-organic frameworks (MOFs) can be utilized as superior precursors to pyrolytically achieve the single-atom catalysts. However, most of the atomic active sites are buried inside the microporous carbon matrix, which severely impedes the accessibility of active sites and limits mass transport. Herein, the mesoporous carbon nanoframes with hierarchical pore size distribution and atomically dispersed Fe-N-x active sites were synthesized from Fe-doped MOF precursors. The dense Fe atoms within the nanostructures are dispersed in single-atom level with metalloporphyrin-like Fe-N-4 configuration. The introduction of plentiful large mesopores into the nanoframes would not only enhance the accessibility of abundant single-atom active sites, but also boost mass and charge transports. Such distinctive nanostructure led to exceptional bifunctional electrocatalytic performances for oxygen reduction reaction, with more positive onset potential (1.01 V vs. 0.97 V) and half-wave potential (0.89 V vs. 0.82 V) compared with the commercial Pt/C, and electrochemical carbon dioxide reduction.