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

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.