# Breaking the ORR Trade‐Off via Mg‐Steered Fe‐N4 Pyridinic Conversion

## TL;DR

This paper introduces a strategy using magnesium to improve the performance and durability of iron-based catalysts for oxygen reduction reactions.

## Contribution

A Mg-assisted strategy is introduced to convert unstable Fe-N4 sites into stable pyridinic-N ligands, enhancing both activity and durability.

## Key findings

- The Fe(Mg)-N-C(1) catalyst achieves a half-wave potential of 0.91 V for ORR.
- The catalyst retains 95.2% of its initial current after 55 hours, outperforming Pt/C.
- It enables stable Zn-air battery operation for over 530 hours with a peak power density of 271 mW cm−2.

## Abstract

Single‐atom Fe sites coordinated by pyrrolic nitrogen (Fe‐Npyrr‐C) are highly active for the oxygen reduction reaction (ORR) but suffer from rapid demetalization‐induced deactivation. Here, we overcome this limitation via a Mg‐assisted sacrificial templating strategy that precisely reconstructs Fe‐N4 coordination, driving partial conversion of unstable pyrrolic‐N to robust pyridinic‐N ligands. The resulting Fe(Mg)‐N‐C(1) catalyst exhibits exceptional ORR performance (half‐wave potential E1/2 = 0.91 V) and outstanding durability, retaining 95.2% of its initial current after 55 h, surpassing both Fe‐N‐C and Pt/C. In Zn‐air batteries, it enables stable operation for > 530 h (peak power density: 271 mW cm−
2). This work demonstrates that enriching pyridinic‐N‐coordinated Fe‐N4 sites simultaneously enhances activity and suppresses demetalization, offering a general coordination‐engineering strategy to unify activity and stability in Fe‐N‐C electrocatalysts.

A Mg‐assisted sacrificial templating strategy is developed to selectively regulate the coordination environment of Fe–N4 sites. This approach induces an active site conversion from S1 to S2, enabling enhancement of oxygen reduction activity and durability.