Fitting Scattering Profiles of Perfluorinated Sulfonic Acid Ionomer Dispersions

Polymer electrolyte fuel cells (PEMFCs) are key to developing the hydrogen economy, particularly in the transportation sector. The focus on heavy-duty vehicles has driven research toward improving the efficiency and durability of catalyst layers and understanding the role of the ionomer binder. The characterization of these ionomers is important not only in their cast forms but also in inks and dispersions. Small-angle scattering (SAS) techniques have become one of the primary tools for analyzing ionomer systems in solution. While SAS can provide valuable structural information about ionomer aggregates, relevant size and shape information requires model fitting to obtain. While many scattering form factor models have been applied to uncover the behavior of aggregates in ionomer dispersions, the role of the fitting range in the fit quality has not been extensively discussed. In this work, we illustrate the effect of varying fitting ranges for three commonly used form factors.