Covalently crosslinked poly (p-terphenyl N-methylpiperidine) based anion exchange membranes for low temperature direct ammonia fuel cells
Zhilin Jiao, Yangkai Han, Tingting Wang, Jianhao Dong, Yun Zhao, Jingshuai Yang
Abstract
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 °C. Additionally, PTP-VBC-20 exhibits excellent alkaline resistance, with almost no loss of conductivity after 500 h in 1M KOH at 70 °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 × 10 −7 cm 2 s −1 ) compared to methyl quaternized membrane (PTP-Me) (P = 1.96 × 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 °C under an operating pressure of 2 bar when a 3 M NH 3 -KOH solution is fed to anode.