Rational design protocols to tune the morphology and conductivity of poly(arylene alkylene)-based anion exchange membranes

Abstract

Constructing efficient ion transport channels in an anion exchange membrane (AEM) by morphology regulation is a wise solution to boost its ion conductivity. Herein, we present a versatile design paradigm for poly(arylene alkylene) AEMs to achieve nanoscale phase separation morphologies by randomly tethering a super-hydrophobic fluorocarbon side chain as well as a tandem triple-cation pendant. The AEM showed excellent conductivities up to 231 mS cm−1 (OH− form) and 75 mS cm−1 (Cl− form) at 80 °C, which is a 2.3-fold boost compared with the poly(biphenylene alkylene) counterpart bearing a terminal quaternary ammonium-contained side chain alone. Moreover, a remarkably high ion diffusion coefficient through the membrane was also observed with the value of 3.7 × 10−6 cm2 s−1. A single cell assembled from perfluoroheptyl pedant-based membrane showed a peak power density of 0.54 W cm−2, and over 92% voltage retention was observed during a 50-h durability test. The results of this study provide a feasible synthetic strategy that will guide the morphological regulation of polyarylene polyelectrolytes to improve the ionic mobility and conductivity.