Quaternary ammonium-functionalized crosslinked poly(aryl ether sulfone)s anion exchange membranes with enhanced alkaline stability for water electrolysis

Quaternary ammonium-functionalized anion exchange membranes (AEMs) have important potential application value in water electrolysis. In order to further improve the ionic conductivity and stability of AEMs, a series of crosslinked AEMs based on poly (aryl ether sulfone)s (Co-PAES-QA-x-m, “x” represents the functionalized polymer segment, “m” represents the crosslinking ratio) are prepared by introducing dense quaternary ammonium cations on the side chains via Menshutkin reaction. Their polymer structures are characterized by hydrogen nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy FT-IR, and the microscopic phase separation structure of the obtained membranes is observed by atomic force microscope AFM. The ion exchange capacity (IEC) of Co-PAES-QA-x-m (x = 25%, m = 40%–100%) is between 2.03–2.48 mmol g−1, and their water uptake (WU), swelling ratio (SR) and ionic conductivity are in the range of 26.9–56.7%, 6.3–12.9% and 53.43–119.43 mS cm−1 at 80 °C, respectively. The test of chemical stability show that the ionic conductivity retention ratio of these AEMs reaches 84.7% after soaking in 2 mol L−1 NaOH solution for 480 h at 80 °C. The water electrolyzer assembled with representative Co-PAES-QA-25-60 reaches 1646.7 mA cm−2 in 2 mol L−1 NaOH solution at 2.0 V and 80 °C, and the durability test shows that its voltage only rises by 5% after 480 h at the current density of 500 mA cm−2. This work is expected to provide an effective modification method for high-performance AEMs which are used in water electrolyzer.