Preparation and characterization of ammonium-functionalized polysulfone/Al2O3 composite membranes

In the current study, a quaternary ammonium polysulfone/Al2O3 composite anion exchange membrane was prepared. This membrane was synthesized using different Al2O3 powder loadings (1–4 wt%) and a casting procedure to avoid the use of hazardous materials. The ammonium-functionalized polysulfones were characterized using 1H NMR and FTIR analyses, and the presence of Al2O3 in the polymeric matrix was confirmed by EDS. The resulting composite membranes exhibited high thermal stability for typical fuel cell operation temperatures below 100 °C. The presence of Al2O3 increased the water absorption and the ion exchange capacity of the membranes. The ionic conductivity of the membranes in dilute aqueous solutions of potassium hydroxide (10−4–10−1 M) was studied using impedance spectroscopy. The results indicated that the ionic conductivity was twice as high when a loading of 4 % Al2O3 was added. The activation energies for ionic transport ranged from 58 to 63 kJ mol−1. The introduction of Al2O3 significantly increased the mechanical strength but decreased the elongation at break, indicating an interaction between the inorganic nanoparticles and the polymer. Therefore, these results suggest that these composite membranes have the potential for use as solid anion exchange electrolytes in low temperature fuel cells.