Elemental Selection Rather than Entropy in Designing Low-Pt High-Entropy Intermetallics for Efficient Oxygen Reduction

Abstract

High-entropy materials (HEMs) have emerged as promising candidates for electrocatalysis. However, their design has largely focused on a higher configurational entropy while neglecting the decisive role of elemental identity. Here we demonstrate that elemental selection, rather than entropy maximization, governs the catalytic performance of high-entropy intermetallics (HEIs) toward the oxygen reduction reaction (ORR) in proton-exchanged membrane fuel cells (PEMFCs). Guided by theoretical calculations, we designed a low-Pt-loading HEI electrocatalyst, HEI-Pt4PdFeCoNi, featuring an ordered L10 structure with a moderate entropy level, an optimal d-band center (−2.433 eV), and pronounced compressive strain (11%). Owing to its electron-rich Pt surface and stabilized intermetallic framework, HEI-Pt4PdFeCoNi delivered ORR activity (E1/2 = 0.932 V and mass activity = 1.244 A mgPt–1 at 0.9 V vs RHE) and negligible degradation after 100,000 potential cycles. In membrane electrode assemblies (MEAs) under H2/air conditions, it achieved a current density of 1.29 A cm–2 at 0.67 V and maintained 98.7% of its initial performance over 1500 h. Even after 150,000 accelerated stress cycles, the mass activity and current density decreased by 9% and 7%, respectively, corresponding to a projected lifetime of ∼61,440 h and a stack cost as low as 121.47 $/kWnet. Mechanistic studies revealed that the performance originated from optimized *OOH adsorption and facilitated O–O bond cleavage, induced by compressive strain and interelement electron transfer. This study establishes elemental configuration of entropy as a governing design principle for L10 Pt-based high-entropy intermetallic ORR electrocatalysts beyond entropy stabilization.