High performance composite membranes with enhanced dimensional stability for use in PEMFC

Sulfonated poly(sulfide sulfone) (SPSSF)/porous polytetrafluoroethylene (PTFE) reinforced composite membranes were prepared from a mixed solvent containing n-butanol and DMSO. To improve their dimensional stability, SPSSF/PTFE membranes were further oxidized to obtain sulfonated poly(phenylene sulfone) (SPSO2)/PTFE composite membranes under an optimized H2O2 oxidation procedure in acidic medium. Thin composite membranes with good mechanical stability can be fabricated due to the PTFE reinforcement. SEM and FTIR indicated the sulfonated polymers were fully impregnated into the expanded PTFE. SPSO2/PTFE membranes show better thermal and dimensional stability than SPSSF/PTFE membranes. Both composite membranes exhibited very excellent single cell performance. A maximum power density of 1.34 W cm−2 for the SPSO2/PTFE membrane was obtained at 80 °C and 100 RH%.