High-performance tetracyclic aromatic anion exchange membranes containing twisted binaphthyl for fuel cells

The development of high-performance anion exchange membranes (AEMs) has become more urgent for fuel cells. One of the critical challenges is to prepare AEMs with sufficient ion conductivity and robust alkaline endurance. In this work, bulky twisted binaphthyl units are introduced into the backbones of AEMs by a one-pot superacid-catalyzed polymerization to enhance both the conductivity and stability. The binaphthyl unit can depress the chain packing density and enlarge the free volume of the AEMs, conducing to form well-defined microphase separation and to build well-developed ion-conductive highways. The poly(binaphthyl piperidinium)-based AEM (QABNP) shows the highest OH− conductivity of 135.25 mS cm−1 superior to the poly(quaterphenyl piperidinium)-based AEM (QAQPP) (109.12 mS cm−1). Meanwhile, the QABNP AEM exhibits about 90% conductivity retention after being tested in a harsh alkaline environment (2 M NaOH at 80 °C) for 1080 h. Importantly, the QABNP based single cell possesses the highest peak power density (PPD) of 1.16 W cm−2 at a high current density of 2.37 A cm−2 with a low high frequency resistance (HFR) of 0.04 Ω cm2. This study demonstrates the merits of bulky twisted binaphthyl incorporated in a polymer backbone for improving AEM performances.