Dense Platinum Nanoparticles Confined in Mn-N-C Nanocages for Robust Heavy-Duty PEMFCs

High-loading Pt cathodes are essential for heavy-duty proton exchange membrane fuel cells but suffer from a critical tradeoff between ionomer sulfonate poisoning and nanoparticle instability. Herein, we report a spatial confinement strategy to encapsulate dense Pt nanoparticles (~51.8 wt%) within Mn/N-co-doped mesoporous carbon nanocages (denoted as Pt-MnNC). This architecture excludes bulky ionomers to create an ionomer-shielded environment against sulfonate poisoning, while Mn-Nx-mediated strong metal-support interactions anchor the Pt nanoparticles to prevent agglomeration and further boost durability. In the 5 × 5 cm2 membrane electrode assembly tests, the Pt-MnNC catalyst delivers an exceptional power density of 1.26 W·cm–2 at 2.0 A·cm–2 under high-humidity condition. Notably, it exhibits superior durability with only a 20.8% mass activity loss after 30,000 cycles, significantly outperforming commercial Pt/C, which suffers a 61.6% loss. This work provides a robust pathway to decouple ionomer poisoning from catalyst loading, advancing the development of high-power, durable heavy-duty fuel cells.