Emerging Porous Solid Electrolytes for Hydroxide Ion Transport

Anion exchange membrane fuel cells (AEMFCs) offer several advantages over proton exchange membrane fuel cells, such as the use of a non-precious metal catalyst, but these cells suffer from various issues related to OH^–-conducting electrolytes, including low conductivity and the formation of K₂CO₃ salt. These issues need to be resolved for the widespread use of AEMFCs. Recently, many studies have focused on developing excellent ion-conductive electrolytes using porous materials based on metal–organic and covalent organic frameworks. However, most of this research is biased toward proton-conducting electrolytes; to the best of the authors’ knowledge, reviews addressing OH^–-conducting electrolytes using porous materials have not been reported thus far. This review discusses OH^–-conducting porous crystalline materials and their membranes in terms of different synthetic strategies, conduction mechanisms, and experimental modalities for the design and development of future anion conductive electrolytes in fuel cells.