a fuel cell having a polymer electrolyte membrane containing fluorine atoms distributed along the polymer chains , and metal conductors and / or catalysts , is protected from fluoride ion degradation of the metal components by a fluoride ion sequestering agent fixed in the cell or flowing through the cell . in a preferred embodiment , the fluoride ion scavenger comprises a suitable number of azacrown moieties attached to polymer constituents in the electrolyte membrane or in electrodes .