A stable anion exchange membrane based on imidazolium salt for alkaline fuel cell

A series of poly(arylene ether sulfone) containing bulky imidazole groups (PSf-Im-x) have been successfully synthesized based on a novel monomer 2,2′-bis-(2-ethyl-4-methyl-imidazole-1-ylmethyl)-biphenyl-4,4′-diol (EMIPO). After quaternized by n-bromobutane, these polymers are evaluated for alkaline anion exchange membranes (AEMs). The functional group, 2-ethyl-3-butyl-4-methyl-imidazolium, is employed in these new polymers for reason that attaching bulky groups around the imidazolium ring reduces the access of OH− to imidazolium, which enhances the alkaline stability of the membranes. The membrane with an IEC value of 2.07 possesses ionic (OH−) conductivity of 0.014 S cm−1 at 30 °C and 80% of the ionic conductivity is maintained after treatment in 1 M KOH at 60 °C for 144 h.