Sulfonated poly(ether ether ketone)-based composite membrane for polymer electrolyte membrane fuel cells

The solid proton conductor zirconium phosphate sulfophenylenphosphonate of composition Zr(HPO4)0.65(SPP)1.35 where SPP denotes metasulfophenylenphosphonate was prepared in the amorphous gel form in dimethyl formamide (DMF) and characterized by 31P NMR. The composite membranes of SPEEK up to 50 wt.% of zirconium phosphate sulfophenylenphosphonate content were prepared by introducing the solid proton conductor from the gel. The composite membranes were characterized using FT-IR, powder X-ray diffraction, SEM, DSC/TGA. The proton conductivity of the membranes was measured under 100% relative humidity up to 70 °C. The composite membranes had better thermal stability when compared with that of SPEEK. A three-fold increase in proton conductivity at 70 °C was observed for the composite membrane with 50 wt.% of solid proton conductor. Furthermore, the conductivity results imply that a critical percentage of proton conductor is needed to establish conduction pathways in the polymer matrix.