Catalyst layers (CLs) in fuel cells and electrolyzers are formed by casting colloidal inks composed of ionomer, catalyst supports, and solvent. Several studies have shown that ink formulation significantly impacts performance; however, procedures for formulating inks are not standardized. Here, we test the effect of synthesis and environmental parameters on ink properties. More specifically, this study probes how formulation variables—mixing order, sonication temperature, dilution history, and Ink aging—impact aggregate size, ionomer adsorption, and dispersion stability. Using dynamic light scattering, rheology, and thermogravimetric methods, we characterize the effects of different formulations. We find that ink properties are especially sensitive to precursor mixing order and ink age. Direct addition of concentrated ionomer to the catalyst promotes greater polymer adsorption, while aging further increases ionomer–particle binding. These findings inform ink design strategies for scalable CL fabrication and have broader implications for polyelectrolyte–colloid systems.
