Tailoring the molecular structure of pyridine-based polymers for enhancing performance of anion exchange electrolyte membranes

Abstract

Anion exchange membranes (AEMs) with high ionic conductivity and excellent chemical stability are desired for relevant electrochemical devices. We designed and prepared pyridine based ether free poly (biphenyl pyridine) (PBP) membranes by modifying pyridinium with both hydrophilic and hydrophobic end groups via the Menshutkin reaction. The grafted ethyl trimethyl ammonium and hexyl pendants assisted the formation of well-connected ion transport channels in the membranes according to the results of transmission electron microscopy (TEM). The highest conductivity of 117 mS cm−1 to hydroxide ions and 73 mS cm−1 to bromide ions was achieved, respectively, at 90 °C by the prepared membranes. The conductivity retention rate of the AEMs was within 84–93% after soaking in 1 mol L−1 KOH at 80 °C for 1008 h. The membrane-based single fuel cell exhibited an open circuit voltage of 0.99 V and a peak power density of 241 mW cm−2 at 80 °C by fueling with humidified H2 and O2 without backpressure. The aqueous zinc bromine battery with a composite separator of the polymer impregnated glass fiber achieved 92.6% of the coulombic efficiency. The assembled battery retained 98% of initial capacity after 157 cycles at a current density of 6 mA cm−2.