Deciphering the effect of interfacial dipole between dinuclear Fe sites and oxygen on breaking activity-stability trade-off in acidic oxygen reduction reaction

Curbing the rapid structural degradation of Fe-N-C materials during acidic oxygen reduction reaction (ORR) has been a long-standing challenge in commercializing ORR-based device with long-term stability. Herein, structural deactivation is effectively inhibited via optimizing interfacial Fe-O dipole by introducing the second Fe atom. The elaborately designed Fe double-atom catalysts (Fe DACs), featuring Fe₂N₆ motifs, induce a shift in O 2 adsorption geometry from end-on to bridge configurations for reorienting interfacial Fe-O local dipole ( μ L ) to relieve demetallation. Hence, Fe DACs achieve enhanced operational stability by 10.4 and 31.2 times over Fe 1 N 4 in both single electrode systems and H 2 O 2 -O 2 fuel cells. In-situ measurements and theoretical simulations reveal the origin for the suppression of structural degradation is due to that the optimized Fe-O μ L reduces the tensile stress exerted by the electric field on the Fe-N bond, coupled with intrinsically stable electronic structure in Fe₂N₆ during dynamic structural evolution to stabilize Fe-N bonds.