Nanocomposite membranes made from sulfonated poly(ether ether ketone) and montmorillonite clay for fuel cell applications

Poly(ether ether ketone) (PEEK) was sulfonated at various degrees with sulfuric acid and dissolved in N,N-dimethylacetamide (DMAc). Montmorillonite (MMT) clay was mixed with this solution and solvent-casted on a glass plate. A Fourier transfer infrared (FTIR) experiment of sulfonated samples showed O-H vibration at 3490 cm(-1) and S=O peaks at 1085 and 1100-1300 cm(-1). Thermogravimetry analyzer (TGA) experiments revealed thermal degradation above 240 degrees C. X-ray diffraction (XRD) confirmed almost zero crystallinity for sulfonated PEEK/MMT. When the degree of sulfonation was increased to 80%, ion-exchange capacity, water uptake, and proton conductivity were increased to almost 2.4 meq/g, 75%, and 0.06 S/cm, respectively. Methanol permeability was decreased to 5 x 10(-8) cm(2)/s by the addition of 10 wt % MMT. A sulfonated PEEK/MMT membrane with 62% of sulfonation and 1.0 wt % MMT loading showed membrane selectivity of approximately 8500 compare to 4500 of Nafion 117.