摘要
Proton exchange membrane fuel cells (PEMFCs) are lightweight, sustainable, and clean power sources that offer much promise for renewable energy applications. Nanostructured platinum (Pt) is the essential catalyst component to catalyze the oxygen reduction reaction (ORR) in PEMFCs. To address the Pt abundance issue and to enhance Pt catalysis, Pt is often alloyed with a transition metal (M) (M = Fe, Ni, Co, and so forth). Despite some impressive ORR activities demonstrated on MPt so far, the stabilization of M in the MPt alloy remains challenging in the oxidizing and acidic ORR condition. Here we report hard-magnet core/shell L1 <sub>0</sub> -CoPt/Pt nanoparticles as a highly active and durable catalyst for the ORR in fuel cells. Its catalytic performance surpasses the activity and durability targets set by the US Department of Energy. L1 <sub>0</sub> -CoPt/Pt is a practical catalyst for use in PEMFCs. 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 <sub>0</sub> -CoPt/Pt nanoparticles with 2–3 atomic layers of strained Pt shell for ORR. At 60°C in acid, the hard-magnet L1 <sub>0</sub> -CoPt better stabilizes Co (5% loss after 24 hr) than soft-magnet A1-CoPt (34% loss in 7 hr). L1 <sub>0</sub> -CoPt/Pt achieves mass activities (MA) of 0.56 A/mg <sub>Pt</sub> initially and 0.45 A/mg <sub>Pt</sub> 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 <sub>Pt</sub> 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. Hard-magnet core/shell L1 <sub>0</sub> -CoPt/Pt nanoparticles with 2–3 atomic layers of Pt shell were synthesized and found to stabilize Co effectively in the corrosive fuel cell condition. The strain and ligand effects brought by the stabilized Co dramatically boost Pt catalysis toward oxygen reduction reaction. The L1 <sub>0</sub> -CoPt/Pt catalyst achieved performance that exceeds DOE 2020 target on Pt activity and durability.