Synthesis and characterization of sulfonated poly(ether sulfone) copolymer membranes for fuel cell applications

Sulfonated poly(ether sulfone) copolymers (PESs) are synthesized using hydroquinone 2-potassium sulfonate (HPS) with other monomers (bisphenol A and 4-fluorophenyl sulfone). A series of PESs with different mol% of hydrophilic group is prepared by changing the mole ratio of HPS in the polymerization reaction. The chemical structure and thermal stability of the polymers are characterized by using 1H NMR, FT-IR and TGA techniques. The PES 60 membrane, which has 60 mol% of HPS unit in the polymer backbone, has a proton conductivity of 0.091 S cm−1 and good insolubility in boiling water. The TGA showed that PES 60 is stable up to 272 °C with a char yield of about 29% at 900 °C under a nitrogen atmosphere. To investigate single-cell performance, a catalyst-coated PES 60 membrane is used together with hydrogen and oxygen as the fuel and the oxidant, respectively. Cell performance is enhanced by increasing the temperature. A current density of 1400 mA cm−2 at 0.60 V is obtained at 70 °C.