Synergistic Carbon Support Engineering in Composite Catalyst Layer for High‐Performance PEM Fuel Cells

ABSTRACT This study introduces an innovative composite cathode catalyst layer (CCL) design for proton exchange membrane fuel cells (PEMFCs), combining Pt‐supported by Vulcan carbon (Pt/V) and Ketjenblack carbon (Pt/KB) to overcome mass transport limitations and ionomer‐induced catalyst poisoning. The composite architecture strategically positions Pt/V layer with lower ionomer‐to‐carbon ratio ( I / C = 0.6) near the proton exchange membrane to maximize surface Pt accessibility and oxygen transport efficiency, whereas Pt/KB layer ( I / C = 0.9) adjacent to the gas diffusion layer leverages its porous structure to shield Pt from sulfonate group poisoning and enhance proton conduction under low‐humidity conditions. This synergistic carbon support engineering achieves a balance between reactant accessibility and catalyst utilization, as demonstrated by improved power density, reduced transport resistance, and higher Pt utilization under dry conditions. These findings establish a new paradigm for low‐Pt CCL design through rational carbon support hybridization and ionomer gradient engineering, offering a scalable solution for high‐performance PEMFCs in energy‐critical applications.