Synthesis and characterization of new membranes deriving from sulfonated polyethersulfone for PEMFC applications

Abstract

Two new types of proton exchange membranes used in proton exchange membrane fuel cell (PEMFC) were synthesized from sulfochlorinated polyethersulfone (PES (polyarylethersulfone)–SO2Cl). One, called S-PESB, was obtained by grafting butylphenol in an amount of 0.3 equivalent per monomer unit. The second (S-PESTD) was prepared by cross-linking with 0.1 equivalent of 4,7,10-trioxa-1,13-tridecandiamine. Analysis of thermal properties (thermogravimetric analysis and DSA) and mechanical testing (dynamical and thermomechanical analysis) of the two membranes showed a significant improvement in comparison with unmodified polyethersulfone sulfonic acid (S-PES). Thus, a significant lowering of the glass transition temperature was observed. In addition, a comparative study carried out with the commercial Nafion® membrane gave very similar values of ionic conductivity and a high selectivity of proton transport. A preliminary electrochemical study of membrane/electrode assembly has shown that the elaborated membranes are promising in PEMFC application. Power densities obtained with cross-linked S-PESTD were superior to those of commercial Nafion®, while S-PESB led to comparable values.