Localized stacked hyper branched anion exchange membrane for fuel cell

The micro-structure modulation is crucial to the ion conductivity and physical/chemical stability of anion exchange membranes (AEMs), a key component in low-cost anion exchange membrane fuel cells (AEMFCs). Herein, we report a method for preparing hyper-branch AEMs with localized stacking structure by introducing triethyltriindole (TTI), a bulky π-conjugated aromatic heterocyclic compound with seven-cyclic structure. The high fractional free volume caused by hyper-branch structure, together with the forming of pronounced ion cluster induced by localized stacking of TTI, lead to ultra-high OH− conductivity (>300 mS cm−1@80 °C) of the as-prepared AEMs. The localized stacking also promotes the localized close packing of molecular chain and provides steric hindrance around the ion exchange groups, thereby restricting the swelling ratio and endowing the AEMs with good mechanical property and outstanding alkaline stability (>2000 h in 1 M KOH at 80 °C). Additionally, high peak power densities of 1.45 W cm−2 with platinum-based catalysts, 0.93 W cm−2 with non-precious oxygen reduction reaction (ORR) catalyst and 1.36 W cm−2 with non-platinum hydrogen oxidation reaction (HOR) catalyst are achieved in H2-O2 fuel cell tests, respectively. [Display omitted] •AEMs with hyper branched and localized stacking structure are fabricated by introducing a bulky Π-conjugated monomer.•High FFV and pronounced ionic cluster lead to ultrahigh OH- conductivity of over 300 mS cm−1.•The localized close packing of molecular chains restricts the swelling of AEMs and enhance their mechanical properties.