High-Performance Anion Exchange Membrane Water Electrolyzers Enabled by Highly Gas Permeable and Dimensionally Stable Anion Exchange Ionomers.

Designing suitable anion exchange ionomers is critical to improving the performance and in situ durability of anion exchange membrane water electrolyzers (AEMWEs) as one of the promising devices for producing green hydrogen. Herein, highly gas-permeable and dimensionally stable anion exchange ionomers (QC6xBA and QC6xPA) are developed, in which bulky cyclohexyl (C6) groups are introduced into the polymer backbones. QC6 ₅₀ BA-2.1 containing 50 mol% C6 composition shows 16.6 times higher H ₂ permeability and 22.3 times higher O ₂ permeability than that of QC6 ₀ BA-2.1 without C6 groups. Through-plane swelling of QC6 ₅₀ BA-2.1 decreases to 12.5% from 31.1% (QC6 ₀ BA-2.1) while OH ^- conductivity slightly decreases (64.9 and 56.2 mS cm ^-1 for QC6 ₀ BA-2.1 and QC6 ₅₀ BA-2.1, respectively, at 30 °C). The water electrolysis cell using the highly gas permeable QC6 ₅₀ BA-2.1 ionomer and Ni _0.8 Co _0.2 O in the anode catalyst layer achieves two times higher performance (2.0 A cm ^-2 at 1.69 V, IR-included) than those of the previous cell using in-house ionomer (QPAF-4-2.0) (1.0 A cm ^-2 at 1.69 V, IR-included). During 1000 h operation at 1.0 A cm ^-2 , the QC6 ₅₀ BA-2.1 cell exhibits nearly constant cell voltage with a decay rate of 1.1 µV h ^-1 after the initial increase of the cell voltage, proving the effectiveness of the highly gas permeable and dimensionally stable ionomer in AEMWEs.
(© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)