Conductivity and Mechanical and Thermal Stability of Polyelectrolyte-Functionalized Anion Exchange Membranes

Recent studies have shown that anion exchange membranes (AEMs) surpass cation exchange membranes (CEMs) in that they reduce fuel crossover and facile electrochemical kinetics in alkaline solution which makes possible the use of non-precious metal electrocatalysts. However, the chemical and mechanical stability of AEMs is generally poor compared to CEMs. Our research has focused on developing porous AEMs utilizing a stable, nonconductive polymer (polysulfone) as the structural matrix functionalized with an ion-conducting polyelectrolyte filling the pores. We have synthetized these membranes via a simple phase-inversion process. Preliminary results using electrochemical impedance spectroscopy (EIS) indicate that the membrane conductivity is not always proportional to the quantity of polyelectrolyte in the phase inversion solution, which has led us to believe that non-homogeneous distribution of the polyelectrolyte may be taking place due to the polarity difference of these molecules. These results are shown in Figure 1 [1].

Continuous analysis and study of the conductive properties as a function of the amount of polyelectrolyte will be performed. Surface and cross-sectional images to identify the porous structure of these AEMs, as well as thermal gravimetric analysis (TGA) investigating thermal stability of these membranes will be presented. Finally, water diffusion anisotropy data will be collected by nuclear magnetic resonance (NMR) technique.

Figure 1: Rodríguez. A., Staser, J. (2015). “Synthesis of polyelectrolyte-functionalized anion exchange membranes and conductive, mechanical and thermal properties study”. (Manuscript is currently in progress)