Anion Exchange Membranes’ Evolution toward High Hydroxide Ion Conductivity and Alkaline Resiliency

The development of alkaline fuel cells over the past decade has led to exciting developments in low resistant and alkaline stable anion exchange membranes (AEMs). This Review highlights new material chemistries and macromolecular designs that have fueled AEMs with ionic conductivities greater than 100 mS cm–1, while demonstrating stability for extended periods in base bath solutions of 1 M potassium (or sodium) hydroxide solutions at temperature of 80 °C or greater. The new AEMs have led to AEM fuel cells (AEMFCs) with power density values that exceed 1 W cm–2 with hydrogen and oxygen. AEM research activities are motivated in large part by their prospect to realize fuel cells free of platinum group metals, which is paramount for cost reduction of fuel cell technology. In addition to highlighting the remarkable achievements of AEMs in the past 4 years, this Review discusses future priorities for the scientific community to address in AEM development. These priorities include stability and conductivity under low humidity or dry conditions, resisting carbonation and oxidation, and AEMFC device stability studies.