Ultra‐High Activity and Durability of Low‐Platinum Fuel Cells Enabled by Encapsulation of L1 ₀ ‐PtCo and L1 ₂ ‐Pt ₃ Co Intermetallic Compounds

Abstract Developing high‐performance, durable, and ultralow‐loading platinum (Pt) catalysts for the oxygen reduction reaction (ORR) is crucial for advancing fuel cells. Here, a novel structured alloy catalyst is reported, characterized by Pt‐Co intermetallic compounds with a Pt‐skin, encapsulated by a covalent organic framework (COF) derived carbon support. This unique structure, combining alloy‐induced strain effects and protective encapsulation, leads to exceptional catalytic activity and stability at an ultralow Pt loading of 0.02 mg _Pt cm ⁻² . To be specific, this catalyst exhibits peak power densities of 1.77 W cm ⁻² in fuel cell tests. It demonstrates a state‐of‐the‐art mass activity of 2.15 A mg _Pt ⁻¹ (@0.9 V), which is 5.38 times that of commercial Pt/C (0.40 A mg _Pt ⁻¹ ). More importantly, the fuel cell assembled with this novel catalyst displays exceptional durability, with a voltage degradation of only 9.9 mV after 100,000 cycles at 0.8 A cm ⁻² and a mass activity retention of 85% (1.83 A mg _Pt ⁻¹ ), far exceeding the 2025 initial mass activity (MA) target (0.44 A mg _Pt ⁻¹ ) of DOE by 4.2 times. Notably, the current density at 0.6 V under hydrogen‐air conditions shows only a slight decline after more than 230 h.