Efficient Oxygen Reduction Catalysis on Fe₄ Cluster Site Facilitated by Adjacent Single Atom

The inherent sluggish kinetics of the conventional four-electron transfer pathway fundamentally limits the oxygen reduction reaction (ORR) efficiency. While electronic structure modulation offers potential solutions, developing effective catalytic regulation strategies remains challenging due to elusive structure-activity correlations. In this study, Fe₄ cluster sites are engineered with dual parallel electron transfer channels that enable concurrent O─O bond cleavage and dual oxygen atom protonation. This unique configuration facilitates an optimized two-step double electron transfer mechanism, significantly enhancing ORR kinetics. Synergistic Mn single atom sites, strategically positioned as electron reservoirs, substantially elevate the electron density of Fe₄ clusters while reinforcing Fe─N coordination bonds through charge redistribution. Remarkably, the spatial configuration of Fe₄ clusters at the support periphery minimizes steric confinement effects, allowing simultaneous product desorption and oxygen adsorption - a critical advantage for sustaining continuous catalytic cycles. Through combined experimental and theoretical analyses, it is demonstrated that this dual-channel electron transport system effectively reduces activation barriers for elementary steps while accelerating charge transfer kinetics. This fundamental study establishes a new paradigm for designing high-performance ORR catalysts through multi-site collaborative engineering and reaction pathway optimization.