Synergistic Proton Transport Regulation and Interfacial Anion Adsorption Engineering in ZIF‐8‐Derived PtCu Electrocatalysts for High‐Performance Light and Heavy‐Duty PEM Fuel Cells

Engineering catalyst‐ionomer interfaces is critical for overcoming the coupled kinetic and transport limitations that impede the commercialization of low‐temperature proton exchange membrane fuel cells (LT‐PEMFCs). Herein, a PtCu alloy supported on a zeolitic imidazolate framework‐8‐derived 3D‐hierarchical carbon framework is developed to simultaneously regulate proton transport and interfacial anion adsorption within the catalyst layer. Oxophilic Cu preferentially interacts with Nafion's sulfonate groups, mitigating excessive adsorption on Pt, while the 3D‐hierarchical porous architecture promotes homogeneous ionomer distribution, continuous proton‐conduction pathways, and efficient water transport. Hydrogen underpotential deposition (HUPD) half‐cell analysis across various concentrations of Nafion revealed Temkin‐type adsorption features and demonstrated weakened Nafion adsorption following Cu incorporation, supported by various physical and theoretical analyses. The optimized catalyst exhibits a reduced Tafel slope of 55.8 mV dec − 1 , delivering 0.75 A mg Pt −1 at 0.90 V IR‐free under H 2 ‐O 2 operation, exceeding the U.S. DOE target. Membrane electrode assemblies achieved 1.52 and 1.80 A cm − 2 at 0.70 V under light‐ and heavy‐duty conditions after 30k accelerated stress‐test cycles. Sequential Distribution of Relaxation Time impedance analysis further demonstrates that synergistic regulation of catalyst‐ionomer interactions and proton transport simultaneously mitigates kinetic, ohmic, and mass‐transport losses, providing a general design strategy for high‐performance LT‐PEMFC.