Highly Conductive and Dimensionally Stable Anion Exchange Membranes with Cross-Linked Networks and Interconnected Ion Transport Channels

Anion exchange membranes (AEMs) with high ionic conductivity, good mechanical properties, and dimensional stability are crucial for preparing the corresponding high-performance electrochemical devices, such as anion exchange membrane water electrolyzers (AEMWEs) and anion exchange membrane fuel cells (AEMFCs). In this study, we have developed a series of novel cross-linking AEMs based on two commercial engineering plastics, polybenzimidazole (PBI) and polysulfone (PSF), in which the functionalized PBI (PBI-Pip) was employed as a highly hydrophilic basic polymer and the chloromethylated PSF was employed as a macromolecular cross-linker. The membranes displayed distinct hydrophilic/hydrophobic micro-phase separation given the effective aggregation of the hydrophilic domains, which was driven by the hydrophilic PBI-Pip. In comparison to the reported PBI-based AEMs, the (PBI-Pip)-PSF-3 membrane exhibited higher hydroxide conductivity of 136.1 mS/cm with a much lower swelling ratio of 28% at 80 °C. Furthermore, this membrane demonstrated excellent mechanical properties with the tensile strength at break of 34.56 MPa and elongation at break of 19.2% under wet state. The cross-linking structure and the highly hydrophilic basic polymer were important for the performance of the membranes. After being assembled with (PBI-Pip)-PSF-3, the AEMWE achieved a maximum current density of 3.0 A/cm 2 at 2.0 V at 80 °C and the corresponding AEMFC exhibited a peak power density of nearly 500 mW/cm 2 at 80 °C.