Synergistic Side-Chain Design of Poly(aryl Quinuclidinium) Anion Exchange Membranes for Fuel Cells

Abstract

Anion exchange membrane fuel cells (AEMFCs) offer a route to hydrogen-to-energy conversion. However, the lack of anion-exchange-membranes (AEMs) with desirable performance severely hampers their commercialization. Herein, we design conductive and alkaline-stable AEMs based on poly(aryl quinuclidinium) with two types of side chains, namely fluorine-terminated alkyl chains and quinuclidinium-capped alkyl chains suitable for AEMFC setup. The side chains induce well-formed microphase separation structures and increase free volume, while the stable quinuclidinium cations on the backbone and side chain prevent nucleophilic substitution and Hofmann elimination under high-temperature harsh alkaline conditions. The optimized AEMs combine an ion conductivity of 185.06 mS cm–1 at 80 °C, tensile strength of 55.24 MPa, elongation at break of 11.22%, and retention of essentially all of their ionic conductivity after 1800 h of immersion in 10 M NaOH at 80 °C. The fuel cell incorporating the optimized membrane (QPPTQ-Qui-BF) demonstrates a peak power density of 1432 mW cm–2 at a current density of 2334 mA cm–2 and a cell voltage of 0.614 V at 80 °C. These results indicate that side-chain engineering of poly(aryl quinuclidinium) backbones is an effective route to AEMs for energy conversion devices.