Block poly(aryl-co-alkyl imidazolium) anion exchange membranes with enhanced performance for fuel cell and water electrolyzer applications

Anion exchange membranes (AEMs), which serve as critical components in hydrogen conversion devices, have attracted considerable attention as next-generation energy materials. In this work, flexible alkyl chains were incorporated into rigid polybiphenyl backbones to synthesize a series of block poly(aryl-co-alkyl imidazolium)-based AEMs (denoted as b-PPxPEy-Im) with a well-balanced rigidity–flexibility combination. Owing to their ether-free backbones and stable imidazolium groups, these block AEMs exhibited excellent alkaline stability. The introduction of a block copolymer architecture enabled clear hydrophilic/hydrophobic microphase separation. As a result, b-PP1PE1-Im showed higher conductivity, improved flexibility, increased water uptake, superior device performance, and lower dimensional swelling than its random copolymer counterpart (r-PP1PE1-Im) at a similar ion exchange capacity. The single H 2 /O 2 fuel cell with b-PP1PE3-Im membrane achieved a peak power density of 1.08 W cm −2 at 80 °C. Moreover, an AEM water electrolyzer (AEMWE) system assembled with b-PP1PE3-Im demonstrated promising performance, reaching 2 A cm −2 at 2.24 V and 60 °C. This study offers an effective strategy for designing durable AEMs with well-rounded properties, underscoring their significant potential for application in fuel cells and water electrolyzers.