Colloidal Nafion in Liquid Media: Insight from SANS Analysis and Molecular Dynamics Simulations

Abstract

Colloidal Nafion™ morphology in liquid media plays a critical role in determining the electrode performance of fuel cells and electrolyzers. In this presentation, we demonstrate that commonly reported, cylindrical morphologies of Nafion in liquid media are not ubiquitous among Nafion dispersions and assuming such may provide inaccurate information.1 Here we compare colloidal Nafion™ morphology in N-methyl-pyrrolidone (NMP) and water using small angle neutron scattering (SANS) and all atomistic molecular dynamics simulations (MD).2 Our SANS analyses using model-dependent and model-independent techniques combined with MD simulations demonstrated highly gel-like particles best describe Nafion particles in NMP, which is in stark contrast to the commonly assumed cylindrical morphology. In high dielectric constant dispersants such as water, the cylindrical morphology is a feasible choice to describe the scattering data, however, the particle radius is much lower than previous report (R = 10 Å). MD simulations support the SANS analysis and show that the sulfonic acid groups are fully dissociated and strongly solvated on the outer wall of the particle suggesting that the structure is driven by hydrophobic interactions.References Aldebert, B. Dreyfus, G. Gebel, N. Nakamura, M. Pineri, F. Volino, Macromolecules, 19, 2651-2653 (1986). Jeffrey M. Klein, Cynthia Welch, Sathish Ponnurangam, Atefeh Tarokh, Kunal Karan, Marilyn E. Hawley, Anna Sokolova, Sung-Dae Yim, Rex P. Hjelm, Yu Seung Kim, ACS Macro Letters, 12, 1648-1653 (2023).