A unitized electrode assembly (10; 110; 210; 310; 410) for a fuel cell includes, in addition to an anode catalyst layer (54; 254) and a cathode catalyst layer (56; 256), a polymer electrolyte membrane (52) having an acid functional group normally including H+ ions and an edge seal (66; 166; 266, 366, 466) containing alkali metal ions in a form, concentration, and/or location for delivery and dispersion into the membrane. The edge seal of the unitized electrode assembly is proximate, and typically contacts, the peripheral edge region (68) of the membrane in ion-transfer relation therewith, and alkali metal ions leach into the membrane during fuel cell operation to provide a desired ion exchange in the membrane. The alkali metal ions contained by the edge seal may be Li+, Na+, K+, Rb+, and/or Cs+, and may be included as a dopant with the material of the edge seal during its formation, or may be included as a discrete component of the edge seal, as by an ion-doped strip of membrane material contained by the edge seal. The edge seal thus serves as a “reservoir” of the alkali metal ions for release to the polymer electrolyte membrane for increased durability.