Hard-Magnet L10-CoPt Nanoparticles Advance Fuel Cell Catalysis

Summary 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 L1 0 -CoPt/Pt nanoparticles with 2–3 atomic layers of strained Pt shell for ORR. At 60°C in acid, the hard-magnet L1 0 -CoPt better stabilizes Co (5% loss after 24 hr) than soft-magnet A1-CoPt (34% loss in 7 hr). L1 0 -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