On the stability of anion exchange membrane fuel cells incorporating polyimidazolium ionene (Aemion+®) membranes and ionomers

Abstract

We report the anion exchange membrane fuel cell (AEMFC) performance using commercial, polyimidazolium-based, Aemion+® as both the ionomer and membrane. Aemion+® affords reduced dimensional swelling yet higher water permeance compared to previously reported polybenzimidazolium-based Aemion® membranes and ionomers. Non-reinforced Aemion+® is shown to enhance the properties of Aemion® membranes, and Aemion+® reinforced with a fluorine-free polyolefin substrate is shown to enhance the properties considered important to fuel cell operation with respect to non-reinforced analogues. The highest AEMFC power density of 1.4 W cm⁻² at 70 °C, 250 kP_abs H₂/O₂ was obtained by using a direct membrane deposition (DMD) approach, where an ultrathin 5 μm membrane increased the voltage stability through enhanced water permeation, allowing characterization under these conditions. However, the reinforcement was found to be pivotal in enabling stable AEMFC operation at 80 °C, where a 10 μm-thick reinforced Aemion+® provided 1.1 W cm⁻² power at 80 °C, 300 kPa_abs H₂/O₂. The degradation properties of this material under varied cell temperatures, current densities and RHs are finally examined.