Engineering Porous Mn–N–C with Abundant Mn–N_<i>x</i> Active Sites for Efficient Oxygen Reduction Reaction via a NaCl Encapsulation–Absorption Strategy

Nitrogen-coordinated manganese atoms on carbon materials (Mn–N–C) are promising catalysts for oxygen reduction reaction (ORR); however, their development is hindered by the easy aggregation of Mn atoms during heat treatment. Given this, we present an effective strategy of NaCl encapsulation combined with Mn/N ion absorption to fabricate a high-performance ORR catalyst of Mn–N–C-NaCl-A. The NaCl encapsulation process, which functions as a confined nanoreactor during pyrolysis, reducing the loss of nitrogen precursors, promotes the dispersion of Mn atoms and facilitates the formation of abundant Mn–Nx active sites. Additionally, the hierarchical porous structure, derived from the synergistic effects of micro- and mesopores, enhances mass transport and active site accessibility. Consequently, Mn–N–C-NaCl-A achieves outstanding ORR catalytic activity under alkaline conditions (0.1 M KOH), with a half-wave potential (E1/2) of 0.857 V (vs RHE) and a high limiting current density (JL) of 6.55 mA cm–2, coupled with excellent stability. Furthermore, the liquid-state zinc-air batteries (ZABs) assembled by Mn–N–C-NaCl-A deliver an impressive peak power density of 183.0 mW cm–2, outperforming many state-of-the-art alternatives. This work offers a scalable and cost-effective approach for guiding the development of advanced M–N–C electrocatalysts.