Bis-pyridinium crosslinked poly(ether ether ketone) anion exchange membranes with enhancement of hydroxide conductivity and alkaline stability

A series of tunable bis-pyridinium crosslinked PEEK-BiPy-x anion exchange membranes (AEMs) are prepared successfully to improve the “trade-off” between ionic conductivity and alkaline stability. The crosslinking density of bis-pyridinium is optimized to promote microphase separation and guarantee the free volume. All the PEEK-BiPy-x membranes have a distinct microphase separation pattern observed by atomic force microscopy (AFM) and the PEEK-BiPy-x membranes also display adequate thermal, mechanical and dimensional stability. Impressively, the PEEK-BiPy-0.5 membrane exhibits maximum tensile strength (58.53 MPa) and highest IEC of 1.316 mmol·g−1. Meanwhile, its hydroxide conductivity reaches up to 70.86 mS·cm−1 at 80 °C. Besides, great alkaline stability of PEEK-BiPy-0.5 membrane is obtained with conductivity retention of 91.74% after 1440 h in 1 M NaOH solution, owing to the crosslinked structure of the AEMs and steric effect of bis-pyridinium cations. Overall, the PEEK-BiPy-x membranes possess potential applications in AEMs.