Perfluorinated Ionomer Dispersion Preparation: Autoclaving vs. High-Pressure Homogenizing

Perfluorinated sulfonic acid ionomer (PFSAI) dispersions are widely used for fabrication of ion-conducting membranes and catalyst layers for hydrogen fuel cells. The conformation and concentration of PFSAIs affect the properties of the final product and depend on the liquid phase in dispersion. Here we present a novel method of preparing water/alcohol dispersions based on Nafion and Aquivion PFSAI by using a high-pressure homogenizer. The proposed route is faster and much safer and allows achieving higher PFSAI concentrations in comparison with the autoclave technique used for commercial dispersion preparation. The comparison of dispersion viscosity and PFSAI aggregate size was performed for both techniques and demonstrated similar values. Analysis of the morphology of membranes obtained from different dispersions by the casting method revealed differences in structure, which disappeared after annealing. These results highlight an important novel method of preparing PFSAI dispersions and the use of membrane morphology analysis for membrane quality evaluation.