Enhanced PEMFC Performance and Durability Enabled by a Highly Oxygen-Permeable Ionomer Binder

The long-term operation of proton exchange membrane fuel cells (PEMFCs) is hindered by performance degradation driven by Pt particle growth and agglomeration, as well as ionomer decomposition and redistribution, which reduce the electrochemical active surface area (ECSA) and catalytic site accessibility, limiting PEMFC durability and performance. To address these challenges, a highly oxygen-permeable ionomer (HOPI) is synthesized. Evaluated in rotating disk electrode (RDE) and membrane electrode assembly (MEA) systems, HOPI exhibited enhanced electrochemical performance, with a peak power density of 110 mW cm^-2, higher than Nafion-based MEAs, and attributed to HOPI's high oxygen permeability and the more porous cathode catalyst layer (CCL) microstructure it forms. HOPI-MEAs also showed a superior durability. After 50 h of accelerated durability testing, HOPI-based CCLs retained their thickness without significant change, while Nafion-based CCLs underwent nonuniform thinning. Characterization revealed that HOPI suppressed Pt aggregation and particle growth more effectively than Nafion, preserving ECSA and active site accessibility and demonstrating HOPI as a promising binder for high-performance, durable PEMFCs.