For robust anion exchange membranes, we have investigated the effect of aliphatic side chains on the properties of partially fluorinated aromatic copolymers (QPAFs) with ammonium groups. A new series of QPAF membranes with various interstitial aliphatic side chain lengths (QPAF-Cx) where x = 2-6 were successfully synthesized. QPAF-C3 with a propylene side chain and ion exchange capacity (IEC = 1.24 meq. g-1) showed balanced properties with the highest hydroxide ion conductivity (99 mS cm-1 at 80 °C in water) and relatively low water uptake, based on a well-developed phase separated morphology. Moreover, the QPAF-C3 membrane exhibited excellent alkaline stability to maintain high ion conductivity (98% remaining) and high mechanical properties after 1000 h in 1 M KOH at 80 °C. The QPAF-C3 membrane also revealed reasonable stability even in 4 M and 8 M KOH at 80 °C. In fuel cell operation, the QPAF-C3 membrane exhibited a higher power density (224 mW cm-2) than those of our previous QPAF-C1 (138 mW cm-2), QPAF-C1B (167 mW cm-2), and Tokuyama A-201 (122 mW cm-2) membranes. In the durability test for 62 h, QPAF-C3 maintained 69% of its initial voltage with minor structural degradation.
ASJC Scopus subject areas
- 化学 (全般)