Mn Doping Induced Ordering Transformation and Strain Engineering in a PtCu Alloy for Enhanced Oxygen Reduction Catalysis

Developing active and durable platinum-based catalysts is critical for advancing proton-exchange membrane fuel cells (PEMFCs). To overcome the Cu dissolution and poor stability of PtCu intermetallics, we propose a Mn-doping strategy to fabricate L1₀-ordered PtCuMn nanocatalysts. Mn incorporation modulates the Pt electronic structure, enhances L1₀ ordering, and induces compressive strain within a Pt-rich shell. Consequently, the catalyst demonstrates exceptional oxygen reduction reaction (ORR) activity with a half-wave potential of 0.921 V, a mass activity (MA) of 0.96 A mg_Pt^-1 and a negligible half-wave potential shift after 30 000 cycles. In PEMFCs, it delivers peak power densities of 1.31 W cm^-2 (H₂-air) and 2.23 W cm^-2 (H₂-O₂). Furthermore, its MA reaches 0.78 A mg_Pt^-1, which exceeds the U.S. Department of Energy (DOE) 2025 target. Operando characterizations and theoretical calculations confirm that Mn doping downshifts the Pt d-band center, accelerates the conversion kinetics of the key *OH intermediate, and thereby optimizes the ORR performance.