Covalently crosslinked poly (p-terphenyl N-methylpiperidine) based anion exchange membranes for low temperature direct ammonia fuel cells

Low ammonia permeability and stable anion exchange membranes are crucial for the long-term efficient operation of direct ammonia fuel cells. Here, we present a thermal crosslinking strategy to balance ammonia permeation and dimensional stability of crosslinked poly (p-terphenyl N-methylpiperidine) (PTP-VBC-x). The cross-linked network and ether-free backbone characteristics endow PTP-VBC-20 with excellent dimensional stability and alkali resistance. The PTP-VBC-20 membrane achieves a high conductivity at low ion exchange capacity (IEC = 1.74 mmol g(-1)), with the conductivity of OH- reaching 100.1 mS cm(-1) at 80 degrees C. Additionally, PTP-VBC-20 exhibits excellent alkaline resistance, with almost no loss of conductivity after 500 h in 1M KOH at 70 degrees C, and no degradation of cations is detected through infrared characterization. By controlling hydration and swelling through the crosslinking strategy, PTP-VBC-20 exhibits a lower ammonia permeability (P = 2.09 x 10(-7) cm(2) s(-1)) compared to methyl quaternized membrane (PTP-Me) (P = 1.96 x 10(-6) cm(2) s(-1)). Moreover, the direct ammonia fuel cell based on PTP-VBC-20 delivers a peak power density of 201.7 mW cm(-2) at 95 degrees C under an operating pressure of 2 bar when a 3 M NH3-KOH solution is fed to anode.