Highly ordered, ultra-dense intermetallic nanocrystals extend heavy-duty fuel cell projected lifetime beyond 240,000 h

High-performance cathode catalysts are essential for proton-exchange membrane fuel cells. Intermetallic nanocrystals are promising candidates but suffer from intrinsic activity–durability trade-offs because their comprehensive catalytic properties are determined by several intertwined structural factors that cannot be optimized independently by existing synthesis techniques. The challenge lies in the inherent thermodynamic and kinetic constraints during synthesis. Here we develop a decoupled synthesis strategy that leverages block-copolymer micelle confinement, which enables the customized synthesis of libraries of intermetallic nanocrystals, simultaneously achieving ultra-small size, ultra-high ordering degree, tailorable loading density, narrow size distribution, compositional uniformity, and broad compositional and substrate universality. The developed Pt 3 Co intermetallic nanocrystal/Ketjenblack catalyst achieves a rated power density of 1.08 W cm −2 and 92% rated power retention after 30,000 cycles under light-duty-vehicle conditions and 900 h of stable operation at 10 A. It also delivered a 70.2% cell efficiency without degradation and 98.4% specific power retention after 90,000 cycles of heavy-duty-vehicle applications. This performance led us to project a lifetime of 240,000 h.