Atomic Ordering Regulates Pt Coordination and Interfacial Water in PtCoCu Electrocatalysts

The sluggish cathodic oxygen reduction reaction (ORR) and limited durability of Pt-based alloys remain major challenges for proton exchange membrane fuel cells (PEMFCs). Here, we report a Cu-assisted strategy to construct an ordered L12-PtCoCu intermetallic constructed through Cu incorporation and reductive annealing. The resulting ordered PtCoCu structure exhibits a relatively electron-rich Pt environment, contracted Pt–Co/Cu coordination, and compressive lattice strain. Consequently, L12-PtCoCu/C delivers a half-wave potential of 0.916 V and mass and specific activities of 0.71 A mgPt–1 and 0.98 mA cmPt–2, respectively, at 0.90 V. After 30,000 accelerated durability cycles, its half-wave potential decreases by only 3 mV. In membrane electrode assembly tests, L12-PtCoCu/C achieves peak power densities of 1.25 W cm–2 under H2–air and 2.50 W cm–2 under H2–O2 conditions. Operando synchrotron radiation infrared spectroscopy further reveals pronounced potential-dependent evolution of oxygenated intermediates and restructuring of interfacial water. These results highlight the correlation between atomic ordering, local Pt coordination, interfacial responses, and enhanced ORR performance.