Ultrathin PtCu Nanosheets: A New Frontier in Highly Efficient and Durable Catalysts for the Oxygen Reduction Reaction

Platinum-copper alloy nanosheets supported on carbon (PtCu NS/C) with well-defined (111) facets were synthesized via a scalable one-pot method, yielding ultrathin structures with thicknesses of ∼1 nm and lateral sizes of ∼10-15 nm. As catalysts for the oxygen reduction reaction (ORR), PtCu NS/C exhibited superior performance and durability compared to those of PtCu octahedral nanoparticles (PtCu NP/C) and commercial Pt/C. In half-cell measurements, PtCu NS/C achieved a mass activity of 5.61 A mg_Pt^-1 at 0.9 V_RHE and an electrochemically active surface area (ECSA) of 94 m² g_Pt^-1, significantly surpassing those of PtCu NP/C and Pt/C. In polymer electrolyte membrane fuel cells (PEMFCs), PtCu NS/C delivered a current density of 48 mA cm^-2 at 0.8 V, retaining 31 mA cm^-2 after 50 000 accelerated stress test cycles. The outstanding activity and stability are attributed to the nanosheet architecture, which provides a high surface-to-volume ratio, abundant (111) surface atoms, enhanced Pt utilization, and an enlarged interfacial contact region with the carbon support. These findings highlight the potential of two-dimensional PtCu nanosheets as highly efficient and durable ORR catalysts for PEMFCs.