Side-chain-type anion exchange membranes bearing pendant quaternary ammonium groups flexible spacers for fuel cells

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2016-09, Vol.4 (36), p.13938-13948
• Main Authors: Lin, Chen Xiao, Huang, Xiao Ling, Guo, Dong, Zhang, Qiu Gen, Zhu, Ai Mei, Ye, Mei Ling, Liu, Qing Lin
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c6ta05090e

To realize high performance anion exchange membranes (AEMs) for alkaline fuel cells (AFCs), a series of quaternized poly(ether sulfone)s (PESs) with different lengths of flexible spacers linking cationic groups and the backbone was synthesized via nucleophilic polycondensation, demethylation and Williamson reactions. Atomic force microscopy (AFM) phase images show clear hydrophilic/hydrophobic phase separation for all the side-chain-type AEMs. The PES- n -QA membrane with hexyleneoxy spacers ( n = 6) between the cationic groups and backbone (benzene ring) exhibited the maximum conductivity of 62.7 mS cm −1 (IEC = 1.48 meq. g −1 ) at 80 °C. The AEM materials are found to have an improved long-term alkaline stability by extending the length of the flexible spacer ( n ≥ 4). The PES-12-QA membrane with a flexible dodeceneoxy spacer demonstrated the highest alkaline stability, where the conductivity and IEC only decreased by 8.1% and 6.9% after immersing in a 1 M aqueous KOH solution at 60 °C for 720 h. Furthermore, the single fuel cell performance test using PES-6-QA as an AEM showed a maximum power density of 108.3 mW cm −2 at a current density of 250 mA cm −2 at 60 °C. Highly conductive anion exchange membranes can be achieved by tuning the length of flexible spacer between backbone and quaternary ammonium groups.