Two-Sequential-Kinetics Control Strategy for Field-Enhanced Oxygen Reduction

The sluggish kinetics of the oxygen reduction reaction (ORR)─a critical bottleneck in fuel cells and metal–air batteries─originate from intertwined charge, spin, and coordination constraints, compounded by the high dissociation barrier of the O═O bond. To address these limitations, we engineer a two-sequential-kinetics control strategy, demonstrated by L10-FePt/Fe core–shell nanocatalysts featuring a chemically ordered ferromagnetic L10-FePt core and an epitaxial Fe monolayer shell. The single-atom-like Fe shell reconfigures O2 adsorption from Pauling-type vertical top-site (Fe–O═O) to Yeager-type parallel bridge-site (Fe–O–O–Fe) coordination, optimizing O2 adsorption kinetics. Sequentially, the ferromagnetic exchange-coupled interface induces a spin pinning effect (pinning ratio of 70%) under magnetic fields, which facilitates the spin-selective flip of added electrons, thereby eliminating spin-forbidden kinetic barriers in the spin transition process between the Yeager-type adsorbed triplet O2 (S = 1) and singlet H2O (S = 0) during the ORR. This strategy delivers a 10.9-fold enhancement in specific activity versus that of commercial Pt/C, with transformative implications for spin-constrained electrocatalysis.