Enhancing oxygen transport with ionic liquid-Nafion interaction in membrane electrode assemblies

Local oxygen transport resistance in the catalyst layer, primarily caused by the dense ionomer film near the catalyst surface due to specific adsorption of sulfonate groups (-SO 3 - ), remains a major limiting factor for PEMFC performance. Here, we propose a molecular regulation strategy using an ionic liquid (IL) to mitigate the detrimental effects of Nafion ionomer. IL cations electrostatically interacts with SO 3 − , weakening ionomer adsorption on platinum (Pt) surfaces and promoting hydrophilic–hydrophobic phase separation of the Nafion matrix, creating more amorphous regions that facilitate local oxygen transport. Consequently, the IL-modified membrane electrode assemblies exhibit a 35.3% reduction in local oxygen transport resistance and a 1.41-fold enhancement in peak power density. Furthermore, Coulombic interactions stabilize the IL within the catalyst layer, ensuring a uniform ionomer distribution and enhanced surface hydrophobicity. Thus the electrodes exhibit remarkable durability. This study provides a novel interfacial engineering solution to improve both PEMFC performance and long-term stability.