Long side-chain N-heterocyclic cation based ionic liquid grafted poly(terphenyl piperidinium) membranes for anion exchange membrane fuel cell applications

Abstract

Anion exchange membrane fuel cells (AEMFCs) bring out unique advantages including the use of cheap and plentiful catalytic materials, fast oxygen reduction reaction rate at cathode and low cost of membranes. However, the development of performing and durable anion exchange membranes (AEMs) is still the major challenge for the ultimate industrial adoption of AEMFC. Herein, the ether-free poly(p-terphenyl-co-N-methyl-piperidine) (PTP) is synthesized and employed as the matrix for AEM. Four ionic liquids of long side-chain N-heterocyclic cations bromide are synthesized and chosen as the quaternization reagents for PTP. Thus, four flexible and long side-chain cationic groups grafted PTP based AEMs are fabricated. The effect of end-group cations on the properties of long side-chain AEMs has been investigated systematically. The presence of long side-chain cations endows AEMs with high conductivity and low swellings simultaneously. Among all the membranes, N-methylpiperidinium grafted AEM (PTP-C5-MPi) exhibits the highest alkaline stability owing to ether-free polymer chain, long side-chain linkage and piperidinium cation, which retains 87 % of its original ion conductivity after storage in 1.0 M KOH solution for 2118 h. Furthermore, the H2–O2 fuel cell based on PTP-C5-MPi is performed to determine the technical feasibility.