Characterization of anionic-exchange membranes for direct alcohol alkaline fuel cells

Abstract

Recently, alkaline direct alcohol fuel cells have received increased attention for the following reasons: anion charge carrier (OH) movement from cathode to anode, opposite to the movement of protons in proton exchange membranes (PEM), may lower alcohol crossover and less expensive non platinum catalysts can be utilized. Quaternized polymers such as poly (arylene ether sulfones) are being developed and studied as possible membrane materials for application in alkaline fuel cells.In this work, quaternary ammonium polymers were synthesized in two step sequence, firstly, by chloromethylation of commercial poly-sulfone followed by amination process as reported previously. Different membrane properties such us water uptake, electrical conductivity and Young modulus were evaluated and compared to other membrane materials commonly employed in PEM fuel cells. A quartz crystal microbalance (QMC) was used to measure the water uptake of thin membranes of this material casted over the quartz crystals, and exposed to vapour at different water activities. Conductivity measurements as a function of the water activity were obtained by AC impedance method, while the mechanical properties of the membranes under different conditions (doped and un-doped) were evaluated by nano-indentation using an atomic force microscope (AFM).