Electrochemical coupling in anion-exchange membrane fuel cells: Hydroxide transport, cation degradation, and interfacial electrochemistry

Anion-exchange membrane fuel cells (AEMFCs) offer a route to low-PGM or PGM-free hydrogen-to-electricity conversion by operating under alkaline conditions. Their practical performance, however, is governed by coupled electrochemical processes rather than by membrane conductivity alone. This review examines AEMFC electrochemistry through a reaction-transport-degradation-interface framework. Alkaline electrode reactions are regulated by the electrical double layer, local water/OH − activity, and ionomer coverage, which together broaden the design space for low-PGM and PGM-free catalysts. Hydroxide conduction is analyzed at the molecular level via vehicular and Grotthuss mechanisms, and at the macroscopic level through concentration-gradient diffusion, electric-field migration, and electroosmotic drag. The spatial heterogeneity of these transport processes further influences degradation behavior-non-uniform OH − activity and potential gradients accelerate cation degradation and disrupt hydrated ion channels. At the catalyst-ionomer interface, phenyl-containing ionomer adsorption and hydration imbalance increase interfacial resistance, while EIS/DRT analysis helps distinguish ion-transport, charge-transfer, and mass-transport losses. Through this analysis, the review links membrane hydration, cation stability, and interfacial resistance to AEMFC durability under operating conditions, providing electrochemical descriptors for the design of AEMs, ionomers, catalysts, and membrane-electrode assemblies.