Evaluation of Water in Perfluorinated Anion Exchange Membranes with Different IEC Values

Water is vital to the transport of ion through anion exchange membranes (AEMs). However, excessive water causes a decline in stabilities of AEMs. To better understand the water effect on AEMs, two states of water, bulk-like water and non-bulk-like water, were identified quantitatively in perfluorinated anion exchange membrane with seven IEC values in the range of 0.9-1.89 mequiv.g(-1). Water in the membranes goes through a redistribution process as IEC changes, where non-bulk-like water content increases almost linearly and steadily with IEC; instead, bulk-like water content increases nonlinearly and sharply with IEC. Bulk-like water has a significant effect on the dimensional stability of the AEMs. It is an advisible strategy to increase IEC value from 0.90 to 1.45 mequiv.g(-1) to improve the ion conductivity as well as reasonable dimensional stability of the AEMs.