Electrochemical characterization of sulfonated PEEK-WC membranes for PEM fuel cells

Sulfonated PEEK-WC polymer was obtained according to chloro-sulfonic acid procedure making possible the preparation of different membrane samples with a sulfonation degree from 48 to 90%. Dense membranes were prepared from casting solutions of S-PEEK-WC dissolved in DMF. Proton conductivity measurements were performed on such S-PEEK-WC membranes in a range of temperature from 30 to 120 °C and 100% of relative humidity, reaching 2.5 × 10−2 S cm−1 as the best value at 100 °C and with a sulfonation degree of 90%. In the meanwhile, the open circuit voltage of this S-PEEK-WC membrane (DS = 90%) varied from 0.963 V at 60 °C to 0.802 V at 100 °C, demonstrating that an increase of temperature negatively affects the membrane performance due to the mechanical properties degradation. In this work, a wide experimental campaign was carried out to investigate the electrochemical performances in terms of polarization curves, open circuit voltage and proton conductivity of S-PEEK-WC membranes as well as the fuel crossover and water uptake.