Static and dynamic rheo-impedance characterization of PEMFC catalyst inks

Catalyst layers are critical to the performance and durability of fuel cells. Because the structure of the catalyst layer is strongly influenced by the microstructure, agglomeration state, and interparticle interactions established in the catalyst ink, systematic investigation of ink properties is essential. This study investigates the static and dynamic rheo-impedance responses of catalyst inks prepared with Pt/Ketjen and Pt/Vulcan under varying shear conditions. Impedance measurements were conducted both under shear and in the static state following shear using an in-house rheo-impedance tool. The electronic conduction resistance associated with the Pt/C network was quantified by fitting the impedance spectra to an equivalent circuit model consisting of parallel electronic and ionic conduction pathways. Comparison of the Pt/C network resistance during and after shear revealed a pronounced difference for the Pt/Ketjen ink, whereas no significant change was observed for the Pt/Vulcan ink. Furthermore, increasing shear rate reduced the Pt/Ketjen network resistance, but led to an increase in resistance for the Pt/Vulcan network at high shear rates. These results demonstrate that rheo-impedance analysis provides a powerful means of probing shear-induced structural evolution in catalyst inks and offers valuable insights for ink formulation and processing optimization. • Static and dynamic rheo-impedance behaviors of catalyst inks were investigated. • Particle size and zeta potential were studied to complement rheo-impedance data. • Pt/C network resistance was quantified by fitting impedance to equivalent circuit. • Pt/Ketjen network resistance differed during and after shear, unlike Pt/Vulcan. • Network resistance reduced for Pt/Ketjen but increased for Pt/Vulcan at high shear.