Elastic and Conductive Cross‐linked Anion Exchange Membranes Based on Polyphenylene Oxide and Poly(vinyl alcohol) for H2‐O2 Fuel Cells

A series of cross-linked AEMs (c-DQPPO/PVA) are synthesized by using rigid polyphenylene oxide and flexible poly(vinyl alcohol) as the backbones. Dual cations are grafted on the PPO backbone to improve the ion exchange capacity (IEC), while glutaraldehyde is introduced to enhance compatibility and reduce swelling ratio of AEMs. In addition to the enhanced mechanical properties resulting from the rigid-flexible cross-linked network, c-DQPPO/PVA AEMs also exhibit impressive ionic conductivity, which can be attributed to their high IEC, good hydrophilicity of PVA, and well-defined micro-morphology. Additionally, due to confined dimension behavior and ordered micro-morphology, c-DQPPO/PVA AEMs demonstrate excellent chemical stability. Specifically, c-DQPPO/PVA-7.5 exhibits a wet-state tensile strength of 12.5 MPa and an elongation at break of 53.0 % at 25 °C. Its OH^- conductivity and swelling degree at 80 °C are measured to be 125.7 mS cm^-1 and 8.2 %, respectively, with an IEC of 3.05 mmol g^-1 . After 30 days in a 1 M NaOH solution at 80 °C, c-DQPPO/PVA-7.5 experiences degradation rates of 12.8 % for tensile strength, 27.4 % for elongation at break, 14.7 % for IEC, and 19.2 % for ion conductivity. With its excellent properties, c-DQPPO/PVA-7.5 exhibits a peak power density of 0.751 W cm^-2 at 60 °C in an H₂ -O₂ fuel cell.