Imidazolium-functionalized carbon nanotubes crosslinked with imidazole poly(ether ether ketone) for fabricating anion exchange membranes with high hydroxide conductivity and dimension stability

Abstract

Simultaneously improving the hydroxide conduction capacity and anti-swelling property of anion exchange membranes (AEM) is a big challenge in the field of fuel cells. In this work, the poly (vinyl imidazole) functionalized carbon nanotube (PVI@CNT) was synthesized as a dual functional nanofiller and introduced into the imidazole poly(ether ether ketone) (IPEEK) matrix. The imidazolium groups on the PVI@CNT offer additional ion conducting sites to improve the hydroxide conductivity. The imidazolium groups also react with the IPEEK to form a crosslinking structure along the nanotubes, thus ensuring favorable anti-swelling property. The nanohybrid membrane with 15 wt % PVI@CNT (IPEEK/PVI@CNT-15) shows a maximum conductivity of 121 mS cm−1 at 70 °C, 100% relative humidity (RH). Meanwhile, the crosslinking structure suppresses the swelling degree from 42.0% (pristine IPEEK) to 17.8% (IPEEK/PVI@CNT-15). The single H2/O2 fuel cell performance of the membrane electrode assembly (MEA) with IPEEK/PVI@CNT-15 membrane reveals a high power density of 128.7 mW cm−2. Moreover, the incorporation of the PVI@CNT also enhances the alkali stability and the thermal stability of the nanohybrid membranes.