High-performing anion exchange membranes enabled by diversifying the polymer backbone of quaternized poly(arylene alkylene)s

Abstract

Anion-conducting poly(arylene alkylene)s are one of the most encouraging anion exchange membrane candidates with high alkaline stability for clean energy power generation. However, optimization of their conductivities often relies on the improvement of ion contents. Herein, a simple design strategy of backbone modification is reported, which can modulate the chain packing behavior and increase the free volume by introducing dimethylfluorenylene (DMeF) units into the poly(terphenylene alkylene) backbone, so as to realize the conductivity improvement of the membrane. The average chain spacing of DMeF-incorporated PTFPA membrane is extended to over 5.1 Å from the original poly(terphenylene alkylene) with the value of 4.2 Å. Accordingly, the membrane properties can be effectively modified by varying the contents of DMeF units, and PFTPA-81 containing 81 mol% of DMeF units particularly demonstrates a combination of high ion conductivity (177 mS cm−1), proper water absorption (<90 wt% at 80 °C), and uncompromised alkaline stability (>1000 h in 1 M aq. at 80 °C). Moreover, a H2–O2 fuel cell prototype fabricated from PFTPA-81 achieved a high peak power density of 1.33 W cm−2, and the cell voltage decreased less than 8% (from 0.75 V to 0.69 V) for an in-situ durability test of 30 h.