Designing anion exchange membranes for CO2 electrolysers

New technologies are required to electrocatalytically convert carbon dioxide (CO2) into fuels and chemicals at near-ambient temperatures and pressures more effectively. One particular challenge is mediating the electrochemical CO2 reduction reaction (CO2RR) at low cell voltages while maintaining high conversion efficiencies. Anion exchange membranes (AEMs) in zero-gap reactors offer promise in this direction; however, there remain substantial obstacles to be overcome in tailoring the membranes and other cell components to the requirements of CO2RR systems. Here we review recent advances, and remaining challenges, in AEM materials and devices for CO2RR. We discuss the principles underpinning AEM operation and the properties desired for CO2RR, in addition to reviewing state-of-the-art AEMs in CO2 electrolysers. We close with future design strategies to minimize product crossover, improve mechanical and chemical stability, and overcome the energy losses associated with the use of AEMs for CO2RR systems. Carbon dioxide electroreduction is a promising approach to synthesize chemicals and fuels using renewable energy. This Review explores our understanding of anion exchange membranes — a key component of certain carbon dioxide electrolysers — and outlines approaches to design improved materials.