Bottom‐up Design of High‐Performance Pt Electrocatalysts Supported on Carbon Nanotubes with Homogeneous Ionomer Distribution

Homogeneous ionomer networks are primarily important for the enhancement of fuel cell performance. Here, we report a bottom‐up design of platinum (Pt) electrocatalysts with homogeneous ionomer layers, in which Pt nanoparticles are deposited on carbon nanotubes (CNTs) after sequentially wrapping with polybenzimidazole (PBI) and end‐capped hyperbranched sulfonated macromolecules (E‐HBM) (CNT/PBI/E‐HBM/Pt). E‐HBM, which are proton conductive macromolecules, are homogeneously coated on CNTs owing to the base–acid interaction between PBI and E‐HBM. The durability and oxygen reduction reaction (ORR) results indicate that CNT/PBI/E‐HBM/Pt exhibits higher Pt stability and ORR activity compared with the electrocatalyst without E‐BHM. The Nafion ionomer‐free membrane electrode assembly (MEA) fabricated from CNT/PBI/E‐HBM/Pt (704 mW cm−2) shows higher power density than the MEA from CNT/PBI/Pt with Nafion ionomer (30 wt %, 603 mW cm−2) owing to the unique bottom‐up design resulting in high Pt utilization efficiency.