Anion exchange membranes with well-developed conductive channels: Effect of the functional groups

• Published in: Journal of membrane science 2018-10, Vol.564, p.298-307
• Main Authors: Liu, Fang Hua, Lin, Chen Xiao, Hu, En Ning, Yang, Qian, Zhang, Qiu Gen, Zhu, Ai Mei, Liu, Qing Lin
• Format: Article
• Language: English
• Subjects: Alkaline fuel cells; Anion exchange membranes; Cationic groups; Flexible alkyl spacers
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2018.07.038

To explore the alkaline stability of cationic groups, several investigations have been reported via small molecule model compounds, theoretical calculations or grafting cations to the benzylic positions of the polymer backbones. In this work, anion exchange membranes (AEMs) with various head groups of trimethylammonium (TMA), 1-methylpyrrolidinium (MPY), 1-methylpiperidinium (MPRD), 1-methylimidazolium (Im1) and 1,2-dimethylimidazolium (Im1,2)) flexibly linked to poly(ether sulfone) (PES) backbones are prepared to explore the effect of pendent functional groups. The AEMs tethering MPRD groups are found to exhibit the highest Br− conductivity of 60.4 ± 2.1 mS cm−1 at 80 °C. PES-MPY exhibits the best relative stability and maintains 90.7% and 83.1% of the original ionic exchange capacity (IEC) and conductivity, respectively, after immersed into 2 M NaOH at 60 °C for 672 h. Meanwhile, the alkaline stability is in the order of PES-MPY > PES-MPRD > PES-TMA > PES-Im1,2 > PES-Im1. The maximum power density of a H2/O2 fuel cell using PES-MPRD (109.0 mW cm−2) and PES-MPY (106.5 mW cm−2) is larger than that using PES-Im1 (65.1 mW cm−2). The results provide a guidance for designing high-performance AEMs. [Display omitted] •Various cationic groups are tethered to polymer backbone via long flexible spacers.•Methylpiperidinium-based AEMs show the highest Br− conductivity.•Methylpyrrolidinium-based AEMs have the highest alkaline stability.•The highest power density is obtained for methylpiperidinium-based AEMs.