Preparation and characterization of electrospun sulfonated poly (ether ether ketone) crosslinked strontium for proton exchange membrane / Engku Safiah Engku Indong

Poly ether ether ketone (PEEK)s have been considered as a candidate material for membrane in PEMFC due to their good mechanical strength, high chemical, and thermal stability, and high proton conductivit. Strontium (Sr) cross-linked nanofibrous membranes based on sulfonated polyether ether ketone (SPEEK) were successfully prepared using the electrospinning technique. The degree sulfonation of the SPEEK is 76 % was determined by H1NMR using the area under the peak of the hydrogen shielding at the aromatic ring of the SPEEK. The value of the IEC is 1.92 meq/g and the FTIR showed O=S=O stretching vibrations of SPEEK at 1077 cm-1 and 1249 cm-1 indicate that SPEEK has successfully sulfonated. Metal-polymer physical cross-linked has been proposed as a way to improve the mechanical and chemical stabilities of the electrospun SPEEK membrane which we found in this finding can help to reduce water uptake compared with the non-crosslinked membrane. Physical cross-linked of Sr- SPEEK membranes were fabricated by the immersion process which was then electrospun into nanofibrous membranes. The optimum voltage, feed rate, and tip to collector distance for electrospinning set up were 12 kV, 0.30 mL/h, and 12 cm respectively. The morphologies of electrospun Sr-SPEEK membrane, fabricated under different concentrations of Sr were presented which show up to 6% concentration of Sr was able to be electrospun. The effect of crosslinking and electrospun membranes on water uptake, proton conductivity, and thermal behaviors was characterized. The expected outcome with the addition of a small amount of Sr has decreased the water uptake. On the electrical properties of the electrospun membrane, the conductivity for the sample with 6% Sr weight percentage has given 0.188 S/cm which is about 80% higher than the film cast Nafion-117 at 80˚C as cited before. This particular result is a hallmark of the studies as it shows that a combination of nanostructured with crosslink is proven to work in favor of producing proton exchange membrane fuel cell (PEMFC) which performed much better than Nafion based membrane