Synergizing Single-Atom and Carbon-Encapsulated Nanoparticles of Fe for Efficient Oxygen Reduction and Durable Zn–Air Batteries

Overcoming the sluggish kinetics of the oxygen reduction reaction (ORR) remains a critical challenge for Zn–air batteries. Fe–N/C catalysts have emerged as promising alternatives to precious Pt-based materials. Herein, we report the design and synthesis of carbon-encapsulated Fe nanoparticles decorated Fe–N/C (denoted as FeNPs@Fe–N/C) via controlled pyrolysis. The FeNPs@Fe–N/C catalyst exhibits excellent ORR performance in alkaline media with a half-wave potential (E1/2) of 0.893 VRHE. The strategic integration of carbon-encapsulated Fe nanoparticles substantially improves the catalytic activity of Fe–N/C catalysts. The FeNPs@Fe–N/C as the Zn–air battery cathode delivers an impressive peak power density of 175.7 mW cm–2 and excellent stability over 500 h, surpassing the Pt/C benchmarks. Density functional theory calculations reveal that the carbon-encapsulated Fe nanoparticles facilitate electron transfer to the catalytic site by modulating the d-band center, thereby boosting the ORR activity. This research paves the way for future design strategies integrating nanoparticles and single atoms for efficient electrocatalysis.