Breakthrough in Single Atom Fe Catalysts for Acidic Oxygen Reduction

• • The CS Fe/N–C catalyst achieves a Fe site density of ~1.6 No. nm−2 in curved regions, 60% higher than planar regions (~1.0 No. nm−2), enabling more active sites per area for ORR. • • 97.6% of FeN4 sites are located in the fourth layer of the nanoprotrusions, providing a protective geometric environment that mitigates Fe dissolution in acidic media. • • The curved-surface morphology with ~10 nm diameter and ~4 nm protrusion height creates a unique coordination environment that enhances electronic delocalization and stabilizes the triplet ground state of adsorbed O2, improving ORR kinetics. • • This design addresses the bottleneck of acidic ORR stability, potentially reducing Pt loading by over fivefold in PEMFC cathodes, lowering cost and advancing commercial viability.