Properties of precursor solution cast PFSI membranes with various ion exchange capacities and annealing temperatures

Perfluorosulfonated ionomer (PFSI) membranes were successfully prepared through a novel perfluorinated sulfonyl fluoride (PFSF) solution casting method. Compared with those manufactured by traditional ways, these membranes have a more ordered inner structure, which give them a higher ionic conductivity and chemical stability, as well as a better methanol crossover resistance. It is crucial to choose suitable ion exchange capacity (IEC) values and preparation conditions for the PFSI membrane manufacture, however, related data are unavailable for this newly discovered technique. Herein, to optimize the preparation conditions, membrane properties, including dimensional stability, water uptake, proton conductivity, solubility and methanol permeability, that vary with IEC values and annealing temperatures were systematically investigated. It is found that an IEC value between 0.94 and 1.02 meq g−1 and an annealing temperature higher than 115 °C are preferred. The result provides first-hand data for the high quality PFSI membrane preparation approach and will be instructive for future membrane studies and applications.