Enhanced hydroxide conductivity of imidazolium functionalized polysulfone anion exchange membrane by doping imidazolium surface-functionalized nanocomposites

A new method was proposed to prepare a membrane with regional aggregation of functional groups by incorporating nanocomposites surface-functionalized with a large number of functional groups. Imidazolium surface-functionalized SiO2 (SiO2-Im) nanocomposites were synthesized by the reaction of 1,2-dimethylimidazole, gamma-chloropropyl triethoxysilane and SiO2 nanocomposites. The obtained SiO2-Im nanocomposites were incorporated into imidazolium functionalized polysulfone (PSf-Im) to fabricate composite alkaline anion exchange membranes. The uniform dispersion of nanocomposites in the membrane was demonstrated by SEM. With increasing mass ratio of SiO2-Im from 0% to 20%, hydroxide conductivity of composite membrane dramatically increases at first and then decreases. The composite membrane with 12 wt% of SiO2-Im shows the highest conductivity, e.g., the hydroxide conductivity of the composite membrane based on PSf-Im with functionalization degree of 76% reaches 32 mS cm(-1) (at 20 circle C) that is 68% higher than the membrane's without doping SiO2-Im (19 mS cm(-1)). In addition, adding SiO2-Im has a slight effect on water uptake and swelling ratio of composite membrane. It indicates that doping surface-functionalized nanocomposites is a simple and effective method to enhance the hydroxide conductivity without increasing swelling.