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Abstract: Composite membranes containing ePTFE matrix and short side chain perfluoronated sulfonated ionomers are introduced as electrolytes for proton exchange membrane fuel cell applications. The output voltage at 800mAcm−2 for single cell using composite membrane as electrolyte reaches 0.61V at 95°C under 40% relative humidity whereas it is only 0.41V for cell assembled from pristine short side chain perfluoronated sulfonated membrane at the same condition. The performance of fuel cell stack using composite membrane as electrolyte in kilowatts ranges has been experimentally investigated at 95°C under ambient pressure. With the increase in the inlet gas temperature, the performance of the stack is enhanced. The non-monotonic behavior in instantaneous average voltage of single cells in the stack has been observed and the peak value is appeared at the stack temperature of 90°C. The observed water accumulation phenomena suggest that the decrease in stack performance above 90°C is attributed to the lack of water in the system. The results observed in this study demonstrate that the composite membrane has the potential operating at 95°C under reduced relative humidity to 40%, which is a suitable operating condition for fuel cell vehicle applications. [Copyright &y& Elsevier]