Electrochemical characterisation of sulfonated polyetherketone membranes

The thermal, mechanical and electrochemical characterisation of sulfonated polyetherketone, including fuel cell tests in hydrogen/ oxygen and hydrogen /air are described. In thermogravimetric analysis, PEEK-S membranes lose wa ter up to 150 degrees C and degradation of the sulfonic acid groups takes p lace at ca. 240 degrees C. Thermomechanical analysis of a PEEK-S membrane o f 60 mu m thickness and equivalent weight 625 g/mole shows that the membran e undergoes a shrinkage of 1.5 % up to 140 degrees C. Reversible elongation of 0.6% occurs thereafter up to 180 degrees C. The conductivity: measured by impedance spectroscopy on non-reinforced and on woven-polymer reinforced PEEK-S, is reported as a function of temperature and of relative humidity (RH), and compared with that of Nafion(R)-117. At 100 degrees C and 100% RH the conductivity of PEEK-S is 2 - 5.10(-2) Scm(-1) (depending on thermal h istory), increasing to 0.11 Scm(-1) at 150 degrees C. Polarisation characte ristics of a non-reinforced PEEK-S membrane of 18 mu m thickness at tempera tures up to 110 degrees C under conditions of hydrogen/air and hydrogen/oxy gen are compared. The results of fuel cell (H-2-O-2) tests on composite rei nforced membranes are reported.