Gas-phase dispersion engineering of PtCo intermetallic catalysts with enhanced compressive strain for high-performance PEMFCs

Pt-based alloys demonstrate superior catalytic activity for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), yet their instability due to transition metal leaching poses a critical challenge. While structurally ordered PtM intermetallic compounds (IMCs) exhibit enhanced stability compared to disordered alloys, their conventional high-temperature synthesis often induces particle aggregation and diminished catalytic performance. Herein, we present a solvent-free gas-phase dispersion strategy leveraging the volatility of acetylacetonate precursors to synthesize ordered PtCo IMC nanoparticles (PtCo/C-IMC) with ultrasmall size (3.0 nm) and uniform compressive lattice strain. The PtCo/C-IMC catalyst delivers exceptional ORR activity (0.92 A mg_Pt⁻¹ at 0.9 V) and durability (6.8 % mass activity decay after 100,000 cycles). In H₂-air PEMFCs, it achieves a peak power density of 1.53 W cm⁻² at 0.6 V and demonstrates outstanding operational stability, with voltage losses of only 17 mV (0.8 A cm⁻²) and 21 mV (1.5 A cm⁻²) after 30,000 accelerated durability test (ADT) cycles, surpassing the DOE 2025 targets and outperforming most reported catalysts. Density functional theory (DFT) calculations and post-ADT characterization reveal that the engineered compressive strain strengthens Pt-Co atomic interactions, optimizes the electronic structure, and elevates the vacancy formation energy of Co. These effects enhance both catalytic activity and stability, offering a scalable pathway for the design of advanced PEMFC catalysts.