Dual-cation comb-shaped anion exchange membranes: Structure, morphology and properties

Abstract

Anion exchange membranes (AEMs) are employed as the gas separator and hydroxide ion conductor between the anode and the cathode of alkaline polyelectrolyte fuel cell (APEFC). Highly conductive and stable AEMs are urgently needed in order to achieve satisfactory fuel cell performance. Nevertheless, the low hydroxide conductivity remains major challenge that limits the development and application of APEFC. In order to improve the hydroxide conductivity of AEMs, highly ordered ion conducting channels must be constructed within the membrane matrix. In this study, an AEM with particular polymer structure was designed to achieve fine ion conducting channels by facilitating the hydrophilic-hydrophobic phase separation. Concretely, the side chain of this polyelectrolyte contains two quaternary ammonium groups and terminates with one long hydrophobic tail. Ascribing to the enhanced nano-phase separation ability, inter-connected ion conducting channels were observed by AFM as well as SAXS. A high hydroxide conductivity of 47mS/cm at 25°C and 85mS/cm at 80°C was achieved. In addition, when applied in an APEFC system, the synthesized AEM showed an outstanding peak power density of 369.3mW/cm2. Good alkaline tolerance, lowered water uptake and swelling ratio were also observed attributing to its carefully designed polymer structure.