Sulfonated-fluorinated copolymer blending membranes containing SPEEK for use as the electrolyte in polymer electrolyte fuel cells (PEFC)

A sulfonated-fluorinated, hydrophilic-hydrophobic copolymer was designed and subsequently synthesized using typical nucleophilic aromatic polycondensation. Facile solution casting was then used to develop blend membranes comprised of sulfonated poly (ether ether ketone) (SPEEK). The monomer sulfonation was carried out for the copolymers while PEEK was sulfonated via classical sulfonation. The considerable local concentration of acidic moieties in the hydrophilic polymer promotes the phase separation of the block copolymer, resulting a good phase-separated morphology. The chemical structure, crystallinity, and intermolecular bond stretching of the copolymer membranes were characterized using 1H-NMR, XRD, and FT-IR instrumentations. TGA, DSC and UTM-based thermal and mechanical properties were investigated for the membranes and were increased upon increasing the wt% of SPEEK in the blend. With the wt% of SPEEK increased, the temperature-dependent proton conductivity also increased, reaching a peak value for SFBC-50/SPEEK-20 is 91 mS/cm, which is 2.1 times higher than that of SFBC-50 (43 mS/cm). The activation energy (E_a) required for proton travel through the membranes was calculated according to the Arrhenius equation, and SFBC-50/SPEEK-20 showed a trivial E_a of 12.47 KJ/mol, which is lower than those of SFBC-30 (15.63), SFBC-50 (15.01) and SFBC-50/SPEEK-10 (13.13). The peak power density reached for PEFC containing SFBC-50/SPEEK-20 was 453.86 mW/cm², which is better in compared to power densities of PEFC containing SFBC-50 (134.24 mW/cm²) and SFBC-50/SPEEK-10 (417.00 mW/cm²) membranes.