Poly(isatin-piperidinium-terphenyl) anion exchange membranes with improved performance for direct borohydride fuel cells

In this work, an effective design strategy for anion exchange membranes (AEMs) incor-porating ether-bond free and piperidinium cationic groups promote chemical stability. A series of poly (isatin-piperidium-terphenyl) based AEMs were synthesized by superacid catalyzed polymerization reaction, followed by quaternization. The effect of functionali-zation on the performance of poly (isatin-N-dimethyl piperidinium triphenyl) (PIDPT-x) AEMs was investigated. Highly reactive N-propargylisatin was introduced into the back -bone to achieve high molecular weight polymers (ha = 2.06-3.02 dL g-1) leading to robust mechanical properties, as well as modulating 1.78-2.00 mmol g-1 of the ion exchange capacity (IEC) of the AEMs by feeding. Apart from that, the rigid non-ionized isatin-ter-phenyl segment provides AEMs improved dimensional stability with a swelling ratio of less than 12% at 80 degrees C. Among them, PIDPT-90 exhibited a higher OH- conductivity of 105.6 mS cm-1 at 80 degrees C. The alkali-stabilized PIDPT-85 AEM was presented, in which OH- conductivity retention maintained 85.6% in a 2 M NaOH at 80 degrees C after 1632 h. Afterward, the direct borohydride fuel cells (DBFC) with PIDPT-90 membrane as a separator showed an open-circuit voltage of 1.63 V and a peak power density of 75.5 mWcm-2 at 20 degrees C. This work demonstrates the potential of poly (isatin-N-dimethyl piperidinium triphenyl) as AEM for fuel cells.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, a design strategy for anion exchange membranes (AEMs) incorporating ether-bond free and piperidinium cationic groups was proposed to enhance chemical stability. A series of poly (isatin-piperidium-terphenyl) based AEMs were synthesized, and the effect of functionalization on their performance was investigated. The results showed that the introduction of N-propargylisatin resulted in high molecular weight polymers with robust mechanical properties and adjustable ion exchange capacity (IEC). The AEMs also exhibited improved dimensional stability and high OH- conductivity. The alkali-stabilized AEM demonstrated excellent OH- conductivity retention after prolonged exposure to NaOH. Furthermore, the direct borohydride fuel cells (DBFC) with the AEM membrane as a separator exhibited promising performance. This work highlights the potential of poly (isatin-N-dimethyl piperidinium triphenyl) as an AEM for fuel cells.