Electronic Bridges-Stabilized Fe–Cu Twin-Sites Circumvent Scaling Relationship for Robust Acidic Oxygen Reduction

The acidic oxygen reduction reaction (ORR) as the soul process in proton-exchange membrane fuel cells, faces fundamental limitations due to linear scaling relations (LSR) among adsorption energies at active sites. This intrinsic constraint typically leads to trade-offs between activity enhancement and compromised selectivity/stability. Here, the second-shell coordination engineering was proposed to construct the heteronuclear twin-site FeCu (TW-FeCu) catalyst, that can directly cleave the O–O bond without formation of sluggish *OOH species to disrupt the LSR of intermediate adsorption and minimize the activation energy for O–O bond scission. This well-designed Tw-FeCu catalyst demonstrates superior activity with a half-slope potential (E1/2) of 0.841 V and 4e– selectivity nearly 100% in acidic media, demonstrating promising potential as the energy device of H2/O2 fuel cells (515 mW cm–2). A series of characterizations revealed that second-shell Cu coordination enhances Fe charge distribution via an electronic bridge channel, thereby suppressing metal leaching, while simultaneously enabling a twin-site cooperative coupling pathway to accelerate reaction kinetics. This work establishes a rational design strategy for highly efficient atomically dispersed ORR catalysts that circumvent LSR limitations.