Microwave-Assisted Synthesis of High-Performance Fe–N–C Electrocatalyst for Proton Exchange Membrane Fuel Cells

Pyrolyzed iron and nitrogen codoped carbon materials (Fe–N–C) with atomically dispersed Fe-Nx sites have received extensive attention as a highly promising alternative to Pt for oxygen reduction reaction (ORR), yet there remains a considerable performance gap between them. To further improve the catalytic performance of Fe–N–C catalysts, we herein developed a microwave-assisted method to improve both the active site density (SD) and intrinsic activity, thus achieving outstanding ORR activity. The in situ generated Fe precipitation is beneficial to improve the doping efficiency of Fe and the subsequent formation of synergetic active sites, leading to increased SD. Both the X-ray absorption spectroscopy and operando Raman confirmed the copresence of atomic Fe moieties and nanoclusters, in which the nanoclusters synergically promote the activity of the single atomic sites. The enriched synergetic active sites endow the as-prepared catalyst with excellent performance by showing a current density of 42 mA cm–2 at 0.9 V in a proton exchange membrane fuel cell, approaching the DOE 2025 target. This work not only affords a highly active ORR catalyst but also provides a simple and potentially scale-up approach to Fe–N–C catalysts.