Graphitic-nitrogen-enriched carbon skeleton with embedment of Fe3C for superior performance air cathode in zinc-air battery

Combining catalytic active materials with nitrogen-doped carbon structure has been an effective strategy for designing high-performance electrocatalysts, where N species plays a vital role in modulating the electronic structure of composite material. The N dopant in the carbon structure exists in different states, but it has been ambiguous which type of N structure contributes the most to the overall catalytic activity. Here, Fe3C nanoparticles embedded in graphitic nitrogen-dominated carbon framework (Fe3C@NC) has been successfully fabricated from Fe@ZIF-8 and exhibits excellent oxygen reduction reaction (ORR) ac-tivity and stability. Experiments and theoretical calculations confirm the interaction between Fe3C and N-doped carbon. Moreover, graphitic nitrogen is proved to exhibit the highest promotion contribution among different N states, which can effectively reduce the energy barrier of the potential determining step (from O2 to *OOH) for ORR. The Fe3C@NC composite is applied as the air cathode in a Zn-air battery, which shows a high EOCV (open-circuit voltage) of 1.48 V, a power density of 155.6 mW/cm2, and a specific capacity of 798 mAh/gZn. This work suggests the synergy of Fe3C, N species, and carbon layer in promoting the performance of ORR catalysts. (c) 2022 Elsevier Ltd. All rights reserved.