Stabilizing transition metals (M) in MPt alloy under acidic conditions is challenging, yet crucial to boost Pt catalysis toward oxygen reduction reaction (ORR). We synthesized ∼9 nm hard-magnet core/shell L1₀-CoPt/Pt nanoparticles with 2–3 atomic layers of strained Pt shell for ORR. At 60°C in acid, the hard-magnet L1₀-CoPt better stabilizes Co (5% loss after 24 hr) than soft-magnet A1-CoPt (34% loss in 7 hr). L1₀-CoPt/Pt achieves mass activities (MA) of 0.56 A/mg_Pt initially and 0.45 A/mg_Pt after 30,000 voltage cycles in the membrane electrode assembly at 80°C, exceeding the DOE 2020 targets on Pt activity and durability (0.44 A/mg_Pt in MA and <40% loss in MA after 30,000 cycles). Density functional theory calculations suggest that the ligand effect of Co and the biaxial strain (−4.50%/−4.25%) of the Pt shell weaken the binding of oxygenated species, leading to enhanced ORR performance in fuel cells.

在酸性条件下稳定MPt合金中的过渡金属（M）具有挑战性，但对于促进Pt催化氧还原反应（ORR）至关重要。我们合成了约9 nm的硬磁核/壳L1 ₀ -CoPt / Pt纳米粒子，其中2–3个原子层的应变Pt壳用于ORR。在60°C的酸性条件下，硬磁铁L1 ₀ -CoPt的Co稳定性（24小时后损耗5％）比软磁铁A1-CoPt（7小时内损耗34％）更好。L1 ₀ -CoPt / Pt在80°C的膜电极组件中经过30,000个电压循环后最初达到0.56 A / mg _Pt的质量活度（MA），在30,000次电压循环后达到0.45 A / mg _Pt，超过了DOE 2020年关于Pt活性和耐久性的目标0.44 A /毫克_Pt在30,000个周期后，MA损失小于<40％）。密度泛函理论计算表明，Co的配体效应和Pt壳的双轴应变（-4.50％/-4.25％）会削弱含氧物质的结合，从而导致燃料电池的ORR性能增强。