Functionalization of polybenzimidazole-crosslinked poly(vinylbenzyl chloride) with two cyclic quaternary ammonium cations for anion exchange membranes

Abstract

The anion exchange membranes (AEMs) with both high ionic conductivity and good stability is always the research focus role for the long-term use of AEM fuel cells. A series of the mechanically and chemically stable PVBC/PBI crosslinked membranes, functionalized with N1-butyl substituted BDABCO groups, were designed, prepared and characterized. With the crosslinking by polybenzimidazole (PBI), the membranes showed good flexibility, strength and low swelling ratio (less than 18%). N1-butyl substituted doubly-charged BDABCO was introduced in the AEMs during the crosslinking reaction instead of the traditional dipping method, benefiting from the improvement compatibility between polymers and BDABCO groups. Attributing to the well-developed phase separation between hydrophilic domains and hydrophobic domains, the family of synthesized AEMs exhibited the higher conductivities than that of DABCO based membranes, which was proved by TEM and SAXS. The M-BDABCO-OH-1:3 with high BDABCO content displayed the highest ionic conductivity of 29.3 and 91.4mScm−1 at 20 and 80°C, respectively. The results of alkaline stability showed that the membranes had the superior chemical stability after immersing in a 1molL−1 KOH at 60°C solution for more than 550h. Furthermore, the peak power density of an H2/O2 single fuel cell using the optimized M-BDABCO-OH-1:3 was up to 340mWcm−2 at 0.492V with the EIS consisting of membrane resistance less than 0.1Ωcm2 which was much smaller than the other AEMs. Overall, the developed membranes demonstrated the superior performance and would be a promising candidate material for AEMFCs.