Highly Hydrophilic Sulfonate Betaine-Grafted Zirconia–Polysulfone Composite Membrane for Alkaline Water Electrolysis

Alkaline water electrolysis (AWE) is one of the most effective methods for green hydrogen production, requiring membranes with high ion conductivity and bubble point pressure to conduct hydroxide ions and prevent gas mixing. Herein, we design a zwitterion-functionalized composite membrane (SB-ZrO2/PSf) by grafting sulfonate betaine (SB) groups onto zirconia particles and blending them with polysulfone (PSf). SB groups create a dense hydration layer via electrostatic interactions, improving wettability and suppressing gas crossover. The composite membrane exhibits excellent hydrophilicity with a water contact angle of 61.1°, 30% lower than commercial Zirfon PERL UTP 500, a low area resistance of 0.11 Ω cm2, 57% lower, and a high bubble point pressure of 4.0 bar versus the Zirfon membrane (1.95 bar). The SB-ZrO2/PSf membrane achieves 960 mA cm–2 at 2.0 V and stable operation over 230 h at 500 mA cm–2 in 30 wt % KOH at 80 °C, demonstrating enhanced electrolysis performance and stability.