Anion conductive piperidinium based poly (ether sulfone): Synthesis, properties and cell performance

Abstract

To fulfill most challenging demand for the anion exchange membranes (AEMs) combining long-term stability and high ion conductivity, a series of anion conducive poly (ether sulfone) (PES) functionalized with piperidinium-based quaternary ammonium directly in the backbone, incorporating different lengths of flexible alkyl chains was prepared via nucleophilic polycondensation and Menshutkin reaction. In this present work, a systematic study was conducted to investigate the effect of the extending side chains on various membrane properties. QAPIPPES-6 with an ion exchange capacity of 1.61 meq g−1 possess the laudable dimensional stability (only 10.4%, in-plane direction) and adequate hydroxide conductivity (84.4 mS cm−1) in the fully hydrated state at 80 °C. Atomic force microscopy (AFM) in tapping mode was performed to confirm the well-defined microphase separation occurred when the length of pendant spacers is ≥ 6. However, the extending side chains are founded to increase the risk of undergoing the Hofmann elimination but fail to enhance the steric hindrance effect to preserve the cation groups. Furthermore, a single H2/O2 fuel cell test for QAPIPPES-1 fabricated into a membrane electrode assembly was operated at 60 °C and exhibited a maximum power density of 216 mW cm−2 at a current density of 400 mA cm−2. These findings demonstrate that the piperidinium-functionalized AEMs with flexible pendant chains appear as the promising material in electrochemical energy devices.