N‐Methylquinuclidinium‐Based Anion Exchange Membrane with Ultrahigh Alkaline Stability

Abstract Anion‐exchange‐membrane (AEM) water electrolysis is a promising technology for hydrogen production from renewable energy sources. However, the bottleneck of its development is the poor comprehensive performance of AEM, especially the stability at highly concentrated alkaline condition and temperature. Herein, a new cationic group N‐methylquinuclidinium with enhanced alkaline stability is proposed and hereby a full‐carbon chain poly(aryl quinuclidinium) AEM is prepared. Compared with reported AEMs, it shows ultrahigh comprehensive alkaline stability (no chemical decomposition, no decay of conductivity) in 10 m NaOH aqueous solution at 80 °C for more than 1800 h, excellent dimensional stability (swelling ratio: <10% in pure water, <2% in 10 m NaOH) in OH⁻ form at 80 °C, high OH⁻ conductivity (≈139.1 mS cm⁻¹ at 80 °C), and high mechanical properties (tensile strength: 41.5 MPa, elongation at break: 50%). The water electrolyzer using the AEM exhibits a high current density (1.94 A cm⁻² at 2.0 V) when assembled with nickel‐alloy foam electrodes, and high durability when assembled with nickel foam electrodes.