Colloidal Nafion morphology in 1,2-alkanediols and its impact on membrane and ionomer properties

Abstract

This study explores the morphology of colloidal perfluoro sulfonic acid (Nafion) in 1,2-alkanediol dispersing agents using small angle neutron scattering (SANS) and all-atomistic molecular dynamics (MD) simulations. SANS analysis reveals that Nafion dispersions in diols, ranging from ethylene glycol to 1,2-pentanediol, exhibit cylindrical morphologies with varying aspect ratios. MD simulations further confirm these findings, showing a cylindrical shape in ethylene glycol and a disk-like morphology in 1,2-pentanediol. Additionally, the simulations indicated that in diol-based dispersions, the sulfonic acid groups of Nafion are primarily internalized, whereas in aqueous Nafion dispersions, they are exposed to the outer surface, enhancing interactions with water. These morphological differences are examined for their influence on membrane properties and electrode performance in fuel cell applications. Overall, the study underscores a clear correlation between Nafion colloidal morphology and its solid-state behavior, emphasizing the critical role of Nafion-solvent interactions.