Highly Ion-Conductive and Alkaline Stable Anion Exchange Membranes Containing Bulky Aryl Units and Symmetric bis-Piperidinium Branches

Abstract

The challenge in developing high-performance anion exchange membranes (AEMs) involves achieving high ion conductivity while maintaining sufficient alkaline and mechanical stability. In this work, an aromatic monomer [bis(4′-(1,5-dibromopentan-3-yl)phenyl)-1,4-terphenyl (BBTP)] with a bulky aryl unit and symmetric dibrominated branches was first designed and synthesized. Then, BBTP was used to prepare aryl ether-free AEMs (QPTPDP-x-OH) via the superacid-catalyzed polyhydroxyalkylation and Menshutkin reactions. Due to the several structural advantages of BBTP, QPTPDP-x-OH membranes reached high hydroxide conductivity up to 161.5 mS cm–1 at 80 °C while maintaining good dimensional stability. Moreover, the membranes exhibited high alkaline stability with the conductivity retention above 80% after soaking in 5 M NaOH at 80 °C for 1200 h. In addition, QPTPDP-30-OH membranes achieved a peak power density of 407.8 mW cm–2 in H2–O2 fuel cells at 60 °C. The design strategy used in this work provided insights into the development of next-generation AEMs with high performance.