Ionomers for PEMs

Proton exchange membrane (PEM) fuel cells incorporate a polymer electrolyte membrane, a crucial component that serves both as the electrolyte and a separator to prevent direct physical mixing of the hydrogen and the oxygen. The polymer electrolyte material contains ionizable groups, usually a metal sulfonate or sulfonic acid. The anionic charge is fixed onto the polymer, and the mobile cations are electrostatically associated with the fixed charges on the polymer. The charge carriers, i.e., protons, migrate through the membrane by “hopping” sequentially from one fixed charge to another.