All‐Aromatic Polymer‐Based Anion Conductive Ionomers with Different Ion Exchange Capacities for Water Electrolysis

Abstract

Anion exchange membrane water electrolysis (AEMWE) is vital for efficient, environmentally friendly, and cost‐effective hydrogen production. Herein, fluorene‐based polymers containing alkyl ammonium groups with different ion exchange capacities (IECs) for use in anion exchange membranes (AEMs) and anion exchange ionomers (AEIs) are investigated. Among the AEMs tested, the AEM with an IEC of 2.2 meq g−1 shows the highest anion conductivity because of its efficient water uptake characteristics. The anode catalyst layers utilize AEIs and iridium oxide catalyst particles. It is essential to select AEIs with appropriate IEC and suitable solvents for high‐performance anodes in water electrolyzers. Morphological and physical property evaluations reveal that moderate hydrophilicity and suppression of water swelling of AEIs improve water electrolysis performance. The optimized catalyst layer achieves better water electrolysis performance (2.64 V, 1.8 A cm−2 at 30 °C) than the conventional catalyst layer (3.83 V, 1.8 A cm−2 at 30 °C). Although the water electrolysis performance in this study falls short of the final targets, further research on anion conductive polymers and catalyst layers, based on this study's findings, is expected to promote practical applications of AEMWEs.