Quaternary Ammonium-Functionalized Polyethylene-Based Anion Exchange Membranes: Balancing Performance and Stability

Anion exchange membrane water electrolyzers (AEMWEs) and fuel cells (AEMFCs) require an anion exchange membrane (AEM) with high hydroxide ion conductivity and high chemical stability to oxidative and alkaline conditions. Herein the conductivities of 17 quaternary ammonium-functionalized polyethylene-based AEMs were measured over time to understand the influence of ammonium functional groups on AEM performance. The piperidinium-based AEM containing a β-methyl in the backbone resulted in a hydroxide conductivity of 41 mS/cm at 22 °C and the highest stability with a 95% conductivity retention after 30 days in 1 M KOH at 80 °C. In fuel cell tests, increasing the ion exchange capacity of the piperidinium-based AEM led to increased performance from a peak power density of 0.7 to 1.0 W/cm2, enabling it to compete with other state-of-the-art AEMs after optimization.