On the Methanol Permeability through Pristine Nafion® and Nafion/PVA Membranes Measured by Different Techniques. A Comparison of Methodologies

Methanol crossover through polymer electrolyte membranes is a critical issue and causes an important reduction of performance in direct methanol fuel cells (DMFCs). Measuring the evolution of CO2 gas in the cathode is a common method to determine the methanol crossover under real operating conditions, although an easier and simpler method is preferable for the screening of membranes during their step of development. In this sense, this work has been focused on the ex situ characterization of the methanol permeability in novel nanofiber-reinforced composite Nafion/PVA membranes for DMFC application by means of three different experimental procedures: (a) potentiometric method, (b) gas chromatography technique, and (c) measuring the density. It was found that all these methods resulted in comparable results and it was observed that the incorporation of the PVA nanofiber phase within the Nafion (R) matrix causes a remarkable reduction of the methanol permeability. The optimal choice of the most suitable technique depends on the accuracy expected for the methanol concentration, the availability of the required instrumental, and the complexity of the procedure.