ION TRANSPORT IN ANION EXCHANGE MEMBRANE FOR ALKALINE FUEL CELL

Alina Amel ¹ Nir Gavish ² Michael Hickner ³ Dario Dekel ⁴ Yair Ein-Eli ¹

¹Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa
²Department Mathematics, Technion-Israel Institute of Technology, Haifa
³Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania
⁴Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa

Quaternary ammonium poly(sulfone)-based anion exchange membrane in Cl^- and HCO₃^- forms was characterized chemically and morphologically. It was found that the membrane in both of the forms has highly connective island-like structure, where the ionic channels are of approximately 5-20 nm diameter size. Thermal gravimetric analysis indicated on some negative influence of the HCO₃^- form on the thermal stability of the side chains and the backbone. In addition, HCO₃^- form demonstrated higher water uptake values than Cl^- form through temperature range of 25-80^oC. Diameter and thickness experiments supported water uptake results. However, conductivity measurements presented higher results for Cl^- form in the temperature range of 25-80^oC under the same experimental conditions. Computational model were built in order to understand the conductivity mechanism and the relevant parameters that limits it. Together with the experimental results it was found that only 40% of ions are free for ionic conductivity, while 60% of the ions are bound to the cationic groups, therefore unavailable to participate in the process.