Tuning Material Properties of Alkaline Anion Exchange Membranes Through Crosslinking: A Review of Synthetic Strategies and Property Relationships

Alkaline anion exchange membranes (AAEMs) are an enabling component for next generation electrochemical applications, including alkaline fuel cells, alkaline water electrolyzers, CO2 electrochemical reduction, and flow batteries. While commercial systems, notably fuel cells, have traditionally relied on proton-exchange membranes (PEMs), hydroxide-ion conducting AAEMs hold promise as a way to reduce cost-per-device by enabling the use of less expensive non-platinum group electrodes and cheaper cell components. AAEMs have undergone significant material development over the past two decades resulting in substantial improvements in hydroxide conductivity, alkaline stability, and dimensional stability. Despite these advances, challenges still remain in the areas of durability, water management, high temperature performance, and selectivity. In this review we discuss crosslinking as a synthesis tool for tuning various AAEM material properties, such as water uptake, conductivity, alkaline stability, and selectivity, and we describe synthetic strategies for incorporating crosslinks during membrane fabrication.