Axial Oxygen-Bridged Dual-Atom Sites Break the Activity-Stability Trade-Off in Oxygen Reduction Electrocatalysis

A pivotal challenge in advancing iron-nitrogen-carbon (Fe-N-C) catalysts for the oxygen reduction reaction (ORR) is their inherent activity-stability trade-off, which originates from the conflicting requirements of strong Fe-N bonding and optimal intermediate adsorption on the Fe active sites. Guided by first-principles screening, we herein report that constructing an axial Fe-O-Co bridge within a bilayer M-N-C architecture concurrently addresses the optimization of intermediate adsorption energetics and dynamic Fe-N bond stability. The competitive adsorption from axial oxygen alleviates the issue of overstrong intermediate adsorption on the Fe site toward accelerated *OH desorption and boosted ORR kinetics. Simultaneously, the axial CoN₄-O ligand serves as an electronic buffer to dynamically compensate for adsorption-induced electronic polarization, thereby stabilizing Fe-N bonds and suppressing iron leaching during electrocatalysis. As a proof of concept, the FeCo dual-atom catalyst featuring an FeN₄-O-CoN₄ configuration achieves a half-wave potential of 0.93 V in alkaline media, with only 8 mV decay after 140 000 cycles, far outperforming the Fe-N-C counterpart (53 mV decay). It maintains remarkable performance even in the highly challenging acidic electrolyte, delivering a peak power density of 1.12 W cm^-2 and nearly 80% power density retention after 30 000 cycles. This study opens up a new avenue to break the activity-stability dilemma for M-N-C catalysts, advancing their practical deployment in fuel cells.