Atomic‐Level CuO _x ‐CoO _x ‐Pd Interfacial Engineering Enables Hierarchical Synergy for High‐Efficiency ORR Pathways and Boosted Power Output in Alkaline Fuel Cells

ABSTRACT The sluggish kinetics of the oxygen reduction reaction (ORR) and the high cost of Pt‐based catalysts remain major barriers for alkaline fuel cell (AFC) technologies. Here we report a Cu‐decorated CoO@Pd catalyst in which atomic‐to‐subnanometer CuO _x species reconstruct the Pd‐Co‐Cu heterointerface and enable a cooperative multi‐site ORR pathway. Structural and spectroscopic analyses reveal that low Cu loading produces atomically dispersed CuO _x motifs that enrich oxygen vacancies (O _V )s, preserve metallic Pd, and stabilize oxygen‐deficient Co ^{3 +} centers. Operando PFY‐XANES/EXAFS further uncovers a synergistic mechanism in which O _V s around Cu serve as rapid O ₂ activation sites, Pd mediates lateral *O ^ads spillover, and O _V s around Co act as the primary *O ^ads reduction centers. This division of labor maximizes four‐electron ORR kinetics, yielding a on‐set potential of 0.935 V and a mass activity (MA) of ∼1.6 × 10 ⁴ mA mg _Cu ^{− 1} without decay for 50k potential cycles, surpassing commercial Pt/C by over two orders of magnitude. When integrated into AFCs, the optimized catalyst (CPCu‐1) delivers a peak power density of ∼430 mW cm ^{− 2} , approximately 60% higher than Pt/C, and exhibits a characteristic three‐stage durability governed by dynamic CuO _x ‐CoO _x interface reconstruction. These findings establish atomic CuO _x interface engineering strategy for designing high‐performance, noble‐metal‐efficient ORR catalysts.