Polyphenylene‐Based Anion Exchange Membranes with Robust Hydrophobic Components Designed for High‐Performance and Durable Anion Exchange Membrane Water Electrolyzers Using Non‐PGM Anode Catalysts

Abstract

Alkaline‐stable, highly conductive anion exchange membranes (AEMs) are attentively expected solid polymer electrolytes that contribute to achieving high performance and durability for anion exchange membrane water electrolyzers (AEMWEs). The technical challenges of AEMs mainly stem from the degradation of the polymer backbones, side chains, and anchoring cationic groups. Herein, new and stable AEMs (QTAF) are designed using 3,3′′‐dichloro‐2′,5′‐bis(trifluoromethyl)‐1,1′:4′,1′′‐terphenyl (TFP) monomers as the hydrophobic component incorporated into the polyphenylene backbone and 3,3′‐(2,7‐dichloro‐9H‐fluorene‐9,9‐diyl)bis(N,N‐dimethylpropane‐1‐amine) (AF) monomers as the hydrophilic component. After tuning the copolymer composition, the highest hydroxide ion conductivity (168.7 mS cm−1 at 80 °C) is achieved with the QTAF‐3.0 membrane. The QTAF‐3.0 membrane survives in harsh alkaline conditions (8 M KOH solution, 80 °C), with high conductivity (75.8 mS cm−1) after 810 h. A water electrolysis cell with QTAF‐3.0 membrane and non‐noble Ni0.8Co0.2O anode catalyst operates stably at a constant current density (1.0 A cm−2) for 1000 h with a negligible voltage increase rate of 1.1 µV h−1 after the initial voltage increase. The water electrolysis performance of the post‐tested QTAF‐3.0 cell is 1.83 V, only a 6.4% increase from the initial performance at 2.0 A cm−2, suggesting the high potential of the QTAF‐3.0 membrane for practical AEMWE applications.