Hydroxide Conductivity and Alcohol Permeability in Anion Exchange Membranes for Fuel Cell Application: Structure–Property Relationships and Design Considerations

Anion exchange membranes (AEMs) have attracted increasing attention for use in direct alcohol fuel cells (DAFCs) due to their ability to conduct hydroxide ions under alkaline conditions while enabling the use of nonprecious metal catalysts. Despite significant advances in polymer chemistry and membrane fabrication, achieving high hydroxide conductivity without excessive alcohol crossover remains a major materials challenge. Enhancing ionic conductivity typically requires higher ion exchange capacity and water uptake, which can increase membrane swelling and facilitate alcohol transport. As a result, hydroxide conductivity and alcohol permeability are closely linked through membrane structure and hydration behavior. This review examines the structure–property relationships that govern these dual transport phenomena in AEMs. Fundamental aspects of hydroxide transport, alcohol sorption and diffusion, and the role of membrane morphology are discussed with emphasis on experimentally observed trends. Polymer design strategies, including control of ion exchange capacity, backbone rigidity, side‐chain architecture, crosslinking, and nanophase separation, are evaluated in terms of their influence on both conductivity and permeability. Stability under alcoholic alkaline conditions and common degradation pathways are also considered. Finally, current challenges in performance comparison and reporting are highlighted, and practical design considerations are proposed to guide the development of next‐generation AEMs with balanced transport properties.