Magnetocrystalline Anisotropic Platinum-Palladium-Iron Ternary Intermetallic Alloy for Enhanced Fuel Cell Electrocatalysis.

Ordered Pt-based intermetallic alloys have emerged as promising candidates for oxygen reduction reaction (ORR) electrocatalysts in comparison to their disordered counterparts. Here, novel ferromagnetic PtPdFe ternary intermetallic alloys with structurally ordered tetragonal L1 and cubic L1 phases are presented, featuring distinctive characteristics in crystal structures and atomic alignments. Insights into the fundamental understanding of the Pt-based ternary intermetallic catalysts are provided, unveiling magnetocrystalline anisotropy as a structure-intrinsic descriptor for ORR catalysis. Electrochemical half- and single-cell assessments reveal that the L1-PtPdFe intermetallic catalysts exhibit superior ORR performance compared to their L1-type counterparts. Combined experimental and theoretical investigations indicate that the unique tetragonal structure of L1-PtPdFe, characterized by strong 5d-3d orbital interactions along the c-axis direction, induces ferromagnetic ordering and leads to increased magnetocrystalline anisotropy energy, thereby accelerating the ORR process. The fuel cell fabricated by such a cathode catalyst retains its performance after prolonged degradation test, meeting the 2025 stability goals set by the US Department of Energy under H-O, H-air, and H-N conditions. These new conceptual findings establish a rational framework for designing high-performance Pt-based intermetallic electrocatalysts, where magnetic anisotropy arising from ferromagnetic ordering can be harnessed to tailor catalytic performance for next-generation fuel cells.