Effect of ionomer content on cathode catalyst layer for PEMFC via molecular dynamics simulations and experiments

The effect of ionomer content on the microstructures and multiphase transport properties of cathode catalyst layer (CCL) for polymer electrolyte membrane fuel cells is investigated via combining molecular dynamics simulations and single-cell experiments. The maximum electrochemical surface area (ECSA) is gained when the Pt/C surface is entirely covered by ionomer due to the established proton transport paths network. As the ionomer content increases in the CCL models, the diffusion coefficient of H3O+ increases by 2 times, while the O2 diffusion coefficient shows decrease monotonously. Both charge transfer resistance and ohmic resistance exhibit U-shaped relationship to ionomer content. It is attributed to the coupling effect of increased ECSA, raised proton diffusion coefficient, and thickening CCL. The effect of ionomer on voltage loss in the low-to-high region is explained via a comprehensive understanding of structural interaction, transport dynamics, ECSA and impedance. It can guide the design of efficient three-phase boundary.