Superior Intermetallic Pt‐Co/C Catalysts With Optimized Triply Metal‐Loading, Size, and Ordering‐Degree for High‐Efficiency and Stable H ₂ –Air Fuel Cells

Pt‐based intermetallic compounds (IMCs) are promising electrocatalysts for oxygen reduction reaction (ORR). This work presents small‐sized (2–4 nm) Pt‐Co IMCs with both high Pt loading (40–60 wt.%) and ordering degree (42%–91%) via an optimized L‐cysteine hydrochloride‐assisted impregnation. Besides heating rate and calcination temperature, metal loading is identified as a critical factor governing IMCs formation. Quantitative XRD analysis reveals that the IMCs fraction reaches 78.8% (29.4% L1 0 ‐PtCo‐IMC + 50.4% L1 2 ‐Pt 3 Co‐IMC) at 40% loading, peaks at 94.5% (68.4% L1 0 ‐PtCo‐IMC + 26.1% L1 2 ‐Pt 3 Co‐IMC) at 50% loading, and declines to 31.6% (solely L1 0 ‐PtCo‐IMC) at 60% loading. The 50% Pt‐Co‐IMCs/C with the highest L1 0 ‐PtCo content delivers the best ORR performance, achieving a mass activity of 0.80 A mg Pt −1 —1.7 times that of commercial PtCo‐TKK. In membrane electrode assembly tests under H 2 ‐air with a low Pt usage of 0.16 mg cm − 2 , a voltage of 0.603 V is achieved at 2.0 A cm − 2 , with only 11.4% voltage decay after 30 000 cycles. Density functional theory calculations corroborate the activity trend of L1 0 ‐PtCo >L1 2 ‐Pt 3 Co >disordered PtCo, thereby rationalizing the loading‐dependent ORR activity. The synergistic effect between optimized * OH desorption kinetics in the rate‐determining step and strong Pt‐Co d ‐ d orbital coupling jointly enhances the activity and stability.