Quantity of saturated adsorbed ionomers on Pt surface in proton exchange membrane fuel cells

Ionomers play a pivotal role in providing a three-phase interface, proton conduction medium, catalyst binder and ink dispersant, which is an indispensable part of PEMFCs. In particular, the ionomer at the three-phase interface promotes the electrochemical reaction, but its specific adsorption on the Pt surface will poison the catalyst and hinder gas transport. Therefore, it is critical to quantify the content of saturated adsorbed ionomers on the Pt surface. In this work, the quantity of saturated adsorbed ionomer on the Pt surface was measured by an electrochemical technique. The calculated ionomer amount corresponding to the saturated adsorption of sulfonates on the Pt surface is only 0.07 (the mass ratio of adsorbed ionomer to carbon), which is independent of the type of ionomer. The spacing limitation and electrostatic repulsion of sulfonate, which can also be defined as the steric hindrance effect of sulfonate adsorption on the Pt surface, is attributed to the almost equal saturated adsorption content for different ionomers. The quantification of the adsorbed ionomer amount on the surface can be used to improve the design of PEMFCs.