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

Abstract

ABSTRACT 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.