Carbon‐Encapsulated PtCo Intermetallic/Co‐N‐C Hybrid Catalyst for Ultralow‐Pt‐Loading Fuel‐Cell Catalysis

ABSTRACT Developing high‐performance, low‐Pt catalysts for oxygen reduction reaction (ORR) is crucial for advancing proton exchange membrane fuel cells (PEMFCs), yet it remains an ongoing challenge. Herein, we report a structurally integrated catalyst featuring PtCo intermetallic nanoparticles encapsulated within a nitrogen‐doped carbon (NC) shell and supported on Co‐N‐C substrate. This catalyst achieves a high mass activity of 1.56 A mg _Pt ⁻¹ at 0.9 V (iR‐free) and retains excellent stability, with only a 4 mV voltage decay at 0.8 A cm ⁻² after 60,000 cycles of accelerated durability testing in PEMFCs, even at an ultralow cathode Pt loading of 0.04 mg cm ⁻² . Through in situ spectroscopy and density functional theory calculations, we identify the mechanisms behind this performance. The NC shell not only acts as a physical barrier to improve stability but also actively promotes reaction kinetics by forming a hydrogen bond (N···*OOH) that breaks the scaling relationship of *OOH/*OH adsorption. Simultaneously, the Co‐N‐C support weakens the *OH adsorption for the optimized ORR kinetics and stabilizes the PtCo intermetallic nanoparticles through reinforcing metal‐support interactions. These synergic effects establish our catalyst as a leading candidate for low‐Pt PEMFCs and demonstrate that the structurally integrated design is a powerful paradigm for creating high‐performance Pt‐based ORR catalysts.