Different cationic functionalized epichlorohydrin modified polyvinyl alcohol based anion exchange membrane

Abstract

Low ionic conductivity and poor alkali resistance have long been the problems of the anion exchange membrane (AEM) of alkaline fuel cell. Herein, epichlorohydrin functionalized by three different cations (piperidine cation, imidazole cation and trimethylammonium cation) are respectively used to modify polyvinyl alcohol (PVA) to prepare a series of PVA based AEMs, and the AEMs are cross-linked by p-phthalaldehyde. ¹H NMR and FT-IR spectroscopy confirm the successful functionalization of epichlorohydrin and the successful preparation of the AEMs. The ion exchange capacity, water uptake, swelling ratio, mechanical properties, thermal stability, OH⁻ conductivity, morphology and alkaline stability of the AEMs are assessed and compared. The experimental results suggest that the AEM modified by piperidine cation owns continuous ion channels and obvious microphase separation structure, resulting in an OH⁻ conductivity of 94.13 mS cm⁻¹ at 80°C. And its alkali resistance is also relatively good (87.16%, 360 h). Besides, crosslinking by p-phthalaldehyde effectively lowers the swelling ratio, increases the thermal stability and improves the mechanical properties of the AEMs.