Polymer electrolyte membranes based on blends of sulfonated polysulfone and PEO-grafted polyethersulfone for low temperature water electrolysis

Polymer electrolyte membranes based on blends consisting of polyethylene oxide (PEO) grafted polyether sulfone (PES-g-PEO) and sulfonated polysulfone (SPSF(Na)) are prepared and their electrochemical and mechanical properties are investigated with respect to water electrolysis operation. The prepared blends are amorphous; they exhibit high glass transition temperatures and high thermal stability, thus ensuring the dimensional stability under electrolysis cell operation. Because of the presence of the water soluble constituent PES-g-PEO, the prepared blend membranes show very high water uptakes, reaching up to 370 wt %. Membrane electrode assemblies are fabricated and evaluated in single cells demonstrating that proton conductivity depends on the PEO-g-PES content as well as the PEO molecular weight. Namely, the increased concentration of PES-g-PEO leads to increased number of charge carriers, thus result in enhanced ionic conductivity. The use of longer PEO units (MW 5000), due to their improved chain mobility, facilitates the fast proton conduction as well. The maximum proton conductivity value is achieved (1.4 × 10−2 S cm−1, 80°C) for the blend with the higher PEO-g-PES content (20 wt %) and the higher PEO molecular weight (5000). Under electrolysis cell operation, the above-mentioned membrane with the lower ohmic resistance shows the best performance, although it is still poor mainly due to the use of Pt as anode. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39922.