Urea‐based construction of hydrogen bonding networks for poly(biphenyl alkylene)s anion exchange membrane for fuel cells

Abstract

In recent decades, the “trade‐off” problem of anion exchange membranes (AEMs) has been a concern. Herein, a series of urea‐based multication poly(biphenyl alkylene)s AEMs are prepared by obtaining an ether bond‐free backbone through ultra‐strong acid catalysis, grafting it with multication side chains, and then by accessing urea‐based groups in different ratios. By accessing the urea group, noncovalent bonds are used to link the molecules to act as cross‐links, giving them solubility that chemical cross‐links do not have. The PBTA‐DQA‐35U membrane possessed the highest ionic conductivity of 62.43 mS/cm. Compared with the PBTA‐DQA membrane (80°C, WU = 20.45%, SR = 17.67%), the PBTA‐DQA‐25U membrane showed an increase in water uptake but not much change in swelling (WU = 30.23%, SR = 19.36%), which was attributed to the fact that the hydrophilic urea groups provide cation transport sites while hydrogen bonding inhibits membrane swelling. The PBTA‐DQA‐35U ionic conductivity is retained above 75% after 960 h of alkali stability testing. The power density of the MEA device assembled using PBTA‐DQA‐35U membrane is 421.78 mW/cm2.