SPEEK/Zeolite/Ionic-Liquid Anhydrous Polymer Membranes for Fuel-Cell Applications

Sulfonated poly(ether ether ketone) (SPEEK)/zeolite/ionic-liquid composite membranes were prepared with different amounts of 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4MI]CF3SO3) or 1-decyl-3-methylimidazolium trifluoromethanesulfonate ([C10MI]CF3SO3) ionic liquids (ILs). The structure of the composite membranes was investigated by FTIR-ATR spectroscopy, X-ray diffraction, atomic force microscopy, and by thermogravimetric analyses. The introduction of the IL, encapsulated in zeolite, into the SPEEK polymer leads to improvement of the water uptake, thermal stability, and proton conductivity of the composite membranes, compared with pristine SPEEK. The proton conductivity of the membranes with 1.5% and 2.0% [C4MI]CF3SO3 IL showed values of 3.34 mS cm(-1) and 5.98 mS cm(-1), respectively, under anhydrous conditions at 80 degrees C. The conductivity obtained for these membranes is about 100 times higher than for pristine SPEEK (0.038 mS cm(-1)).