Advances in anion exchange membranes for electrochemical energy conversion

Anion exchange membranes (AEMs) are playing an increasingly prominent role in enabling practical fuel cells due to rapid advances in materials design and device fabrication. These advances have allowed for the demonstration of record high performance in gas-fed and liquid-fed fuel cells incorporating AEMs. The current state-of-the-art AEMs display high conductivities, high temperature stability (now regularly operating at 80 °C) and mechanical strength that allows for high water uptake and flux without sacrificing structural integrity. On the device front, novel combinations of membrane and binder, optimized using increasingly powerful in-operando probes has led to researchers achieving a clear understanding of rate and lifetime limiting processes. This review briefly surveys the key insights secured over the past decade and subsequently focuses on key results from the past two years that have enabled rapid technological advances. The H2/O2 and NaBH4/H2O2 fuel cells are presented as the model platforms to contextualize these advances while contrasting the challenges faced in gas vs. liquid fuel cells. Further, we examine the incipient research directions that promise to accelerate the advance of AEM technology.