Revealing Robust Atomic Configurations of the Ligand‐Assisted Synthesized High‐Entropy PtIrFeCoNiCu Nano‐Intermetallic Catalysts During Oxygen Reductions in Fuel Cells

Abstract Despite excellent catalytic performance via the “cocktail effect” and the phase stability of high‐entropy alloys (HEAs), their multicomponent surface remains inadequately explored after oxygen reduction reaction (ORR). Moreover, the facile synthesis of nano HEAs is required for practical applications. Herein, nanosized (∼4.8 nm) carbon‐supported PtIrFeCoNiCu intermetallics (PtIr‐iHEA/C), ∼90% ordered, are prepared through a mercaptosuccinic acid (MSA)‐assisted strategy. Combining atomic‐level characterizations and theoretical calculations, the activity is correlated with the evolving surface configuration. Leveraging the activated Pt and Fe sites, PtIr‐iHEA/C displays an initial mass activity (MA) of 1.65 A mg Pt/Ir −1 (0.90 V vs RHE) in rotating disk electrodes (6.9 times that of Pt/C), notably with negligible E 1/2 degradation after 50 000 potential cycles. However, post‐characterizations suggest the cycling induces transition metal (TM) leaching, reconstructing the PtIr‐iHEA@Pt core–shell structure. Theoretical analysis attributes the durable performance tothe electronically optimized rigid Pt shell (active sites) and the strain‐anchored sublayer TMs. Consequently, the fuel cell incorporating PtIr‐iHEA@Pt/C delivers a high mass‐normalized peak power density of 11.6 W mg Pt/Ir −1 (H 2 /Air), and 79% MA retention from 0.75 A mg Pt/Ir −1 after cycling (DOE targets: 0.44 A mg Pt −1 , 60% retention). This study uncovers structure‐performance correlations of Pt‐based iHEA for acidic ORR, enlightening the rational HEA design for broader applications.