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

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Single-atom Fe sites coordinated by pyrrolic nitrogen (Fe-N_pyrr-C) show high activity for the oxygen reduction reaction (ORR).
• These Fe-N_pyrr-C catalysts are prone to deactivation via demetalization, limiting their practical application.
• Developing stable and active ORR electrocatalysts is crucial for energy conversion technologies like fuel cells and metal-air batteries.

Purpose of the Study:

• To overcome the demetalization-induced deactivation of Fe-N_pyrr-C catalysts.
• To enhance the activity and durability of single-atom iron electrocatalysts.
• To develop a general coordination-engineering strategy for Fe-N-C electrocatalysts.

Main Methods:

• A Mg-assisted sacrificial templating strategy was employed.
• Precise reconstruction of Fe-N₄ coordination was achieved.
• Partial conversion of pyrrolic-N to pyridinic-N ligands was induced.

Main Results:

• The resulting Fe(Mg)-N-C(1) catalyst exhibited an exceptional ORR half-wave potential (E_1/2) of 0.91 V.
• The catalyst demonstrated outstanding durability, retaining 95.2% of its initial current after 55 hours.
• Stable operation exceeding 530 hours was achieved in Zn-air batteries with a peak power density of 271 mW cm^-2.

Conclusions:

• Enriching pyridinic-N-coordinated Fe-N₄ sites enhances ORR activity and suppresses demetalization.
• The Mg-assisted strategy effectively unifies activity and stability in Fe-N-C electrocatalysts.
• This approach offers a promising pathway for designing next-generation electrocatalysts for energy applications.