Preparation of crosslinker-free anion exchange membranes with excellent physicochemical and electrochemical properties based on crosslinked PPO-SEBS

Abstract

The process of crosslinking is widely employed to increase the physicochemical stability of anion exchange membranes and, in some cases, improve ion conductivity. For a general case in which a polymer is crosslinked by a crosslinking agent, the physicochemical properties of the polymer can be greatly altered, depending on the type of crosslinking agent. In this study, we induced crosslinking without a crosslinking agent to intentionally maximise various physical properties (i.e., mechanical properties, swelling ratios, and so forth) of two commercially-available polymers. A triazole was incorporated into the conducting group to maximise the ion conductivity, especially under room humidity (RH) conditions. The crosslinked PPO-SEBS membranes prepared through this approach were not only capable of forming very thin membranes (10 μm thickness) with excellent physical properties (34.3 MPa of tensile strength and 91.6% of elongation at break) but also exhibited high hydroxide ion conductivity under 95% RH, and conductivity plays an important role in achieving good fuel cell performance. When the membrane electrode assembly (MEA), as fabricated utilising a crosslinked PPO-SEBS membrane and a platinum on carbon (Pt/C) catalyst on each electrode, was operated in conditions with a H₂/O₂ gas flow and a 60 °C temperature, a stable fuel cell performance was obtained for a long period of time (300 hours) at a maximum power density of 405 mW cm⁻². This result surpasses the performance of commercialized AEMs and is comparable with the performance levels of cutting-edge AEMs when operated under similar conditions.