Multication Cross-Linked Poly(p-terphenyl isatin) Anion Exchange Membranes for Fuel Cells: Effect of Cross-Linker Length on Membrane Performance

Abstract

As a key component of anion exchange membrane fuel cells (AEMFCs), anion exchange membranes (AEMs) have been investigated in the last decades. Herein, a series of multication cross-linkers were introduced into side-chain-type poly(p-terphenyl isatin) to develop high-performance and long-term stable AEMs. Additionally, the effects of the hydrophilic cross-linker length on the membrane performance were systematically investigated. The resulting cross-linked membranes possess a low swelling ratio (<18% at 80 °C) and high tensile strength (51.1−58.3 MPa). Notably, the cross-linker length influences the AEM internal morphology. With hexyl as the spacer between backbones and cation groups in the cross-linker, 0.9q-PTI-6C exhibits the highest hydroxide ion conductivity of 118.5 mS/cm at 80 °C, which is ascribed to well-developed ion channels. Furthermore, alkyl spacer chains and cross-linked networks contribute to the excellent alkali stability of membranes. After immersion in 2 M NaOH for 1200 h at 80 °C, 0.9q-PTI-8C only shows 11 and 12.7% losses in ion conductivity and ion exchange capacity (IEC), respectively. The fuel cell fabricated using 0.9q-PTI-6C can achieve the maximum power density of 310 mW/cm 2 at 80 °C.

Cross-Linked Anion-Exchange Membranes with Dipole-Containing Cross-Linkers Based on Poly(terphenyl isatin piperidinium) Copolymers

“…Except for the peak for air at 3.79 nm –1 , no scattering peak can be found in PTPBHIN-C x and PTPBHIN-O x membranes. The reason may be that the polymer backbones possess high rigidity. , This phenomenon in which the results of SAXS profiles and TEM images are discordant agrees with the previous literature of poly­(arylene) AEMs. ,− …”

“…(a) OH – conductivity of cross-linked membranes after alkali resistance tests. (b) Comparison of alkali resistance of AEMs ,,− ,,,,, (data is presented in Table S1). …”

“…Since the membranes remained insoluble after the alkaline test, their FTIR spectra were obtained to further investigate the causes of membrane degradation (Figure S6). 5,10,[17][18][19]25,31,53,55,56 (data is presented in Table S1). piperidinium groups and the dipole-containing cross-linker may be the reason for a decrease in conductivity of the PTPBHIN-O x membrane.…”

“…Hydrophilic cross-linkers can decrease swelling and increase OH – conductivity simultaneously. ,,, For example, multication cross-linkers were used in AEMs to improve the ion channels of the membranes. In our recent report, we have successfully prepared several tunable multication cross-linked membranes. The resulting 0.9q-PTI-6C membranes exhibited high ion conductivity and low swelling ratio.…”

“…In our recent report, 31 we have successfully prepared several tunable multication cross-linked membranes. The resulting 0.9q-PTI-6C membranes exhibited high ion conductivity and low swelling ratio.…”