Highly stable fuel cell membranes and methods of making them

A solid polymer electrolyte membrane (10) comprises (a) an ion exchange material (12) and (b) dispersed in said ion exchange material, a hydrogen peroxide decomposition catalyst (14) comprising (i) an organic polymer comprising a monomer with at least two carbon atoms and at least one moiety comprising phosphorous, or dihydrogen phosphonate; and (ii) a metal comprising a transition metal with multiple oxidation states or a lanthanide metal with multiple oxidation states.