High-Spin Pt Sites of Intermetallic Compound via Pinning Effect Boost Oxygen Reduction Performance

The commercialization of proton exchange membrane fuel cells (PEMFCs) is hindered by sluggish oxygen reduction reaction (ORR) kinetics at the cathode, demanding high-performance Pt-based catalysts. The ORR efficiency is critically governed by the spin configuration of Pt sites, yet regulating Pt spin states remains challenging due to their inherently paramagnetic nature. Here, we report core-shell L1₀-Pt₂CoFe/Pt₂FeNi intermetallic compounds that achieve stable high-spin Pt sites via a spin-pinning effect. The remanent magnetization of the ferromagnetic core induces a persistent high-spin configuration in the Pt shell after external magnetic field removal. This spin-engineering strategy optimizes Pt 5d orbital splitting, lowering the activation barrier for electron transfer to O₂ and facilitating its activation. Magnetized L1₀-Pt₂CoFe exhibits 8-fold higher mass activity and 31-fold higher specific activity than its nonmagnetized counterpart, outperforming commercial Pt/C. The catalyst also retains 90% of its initial activity after 50 000 cycles and maintains performance after 6 months of storage, demonstrating excellent stability. This field-free spin-pinning strategy offers a practical, generalizable route to designing advanced Pt-based ORR catalysts.