Copper-mediated structural regulation enables ultrasmall L1₀-PtCo_0.5Cu_0.5 ternary intermetallic nanoparticles for...

Pt-based intermetallic compounds are promising oxygen reduction reaction (ORR) electrocatalysts, but achieving atomic ordering while maintaining ultrasmall particle sizes remains challenging because of nanoparticle sintering during high-temperature annealing. Herein, a Cu-mediated structural regulation strategy is employed to construct ultrasmall carbon-supported L1₀-PtCo_0.5Cu_0.5 intermetallic nanoparticles averaging 2.2 nm. The incorporation of Cu regulates atomic diffusion and phase evolution during thermal treatment, facilitating the formation of ordered intermetallic nanoparticles while mitigating excessive particle growth. The resulting L1₀-PtCo_0.5Cu_0.5/C catalyst achieves a mass activity of 1302 mA mg _Pt^-1 in acidic media at 0.9 V, corresponding to an 8.2-fold increase over commercial Pt/C. After undergoing 30,000 accelerated durability test (ADT) cycles, the catalyst retains 91.9% of its initial mass activity, demonstrating outstanding durability. The catalyst also exhibits excellent activity and long-term stability in H₂-air fuel cells. Theoretical calculations combined with experimental analyses reveal that induce electronic redistribution within the PtCoCu framework, optimizing oxygenated intermediate adsorption and reducing the ORR energy barrier. Meanwhile, the strengthened intermetallic framework contributes to enhanced atomic stability, as evidenced by increased vacancy formation energies of Pt and transition-metal sites. The work highlights the advantages of Cu incorporation in the design of ultrasmall Pt-based intermetallic electrocatalysts for PEMFCs.