Low platinum loading catalyst layers for polymer electrolyte fuel cells (PEFCs) consist of a thin film of highly inter-mixed ionomer and catalyst that is applied to the electrolyte membrane. High performances are achieved with loadings as low as 0.12 mgPt cm(-2) at the cathode and even lower loadings are required at the anode. However, the long-term performance of these fuel cells depends upon the structural integrity of the recast, ionomer-bound catalyst layers. The discovery that the inclusion of large cations through a simple ion-exchange process renders perfluorosulfonate ionomers moderately melt-processable is exploited to significantly improve the structural integrity of the catalyst layers. When the thermoplastic form of the solubilized ionomer is used in the membrane catalyzation process, the reproducibility is greatly improved and the long-term performance losses are quite low. Overall, the fuel cells demonstrate less than 10% loss in maximum power over almost 4000 h. An indication of the durability of the catalyst layer and the integrity of the catalyst layer/membrane interface is provided by the high tolerance of such fuel cells to shut-down/start-up and freeze-thaw cycles. Various other aspects of endurance testing and overall operation of such PEFCs are also discussed.