Design of Catalyst/Polyelectrolyte Interfaces for Anion Exchange Membrane Water Electrolysis Under Low‐Concentration Alkaline Conditions

Water electrolysis powered by renewable energy sources is a promising technique for realizing a decarbonized society. Notably, anion exchange membrane water electrolysis (AEMWE) is attracting considerable attention as a technology that enables high energy efficiency using nonprecious metal catalysts. In AEMWE, the design of the interfacial state among the catalyst, ionomer, and anion exchange membrane (AEM) plays an important role in determining cell performance. This interfacial state becomes particularly critical under diluted alkaline operation, where ionic conduction is intrinsically limited; however, systematic studies on catalyst–ionomer–membrane interfaces under such low‐concentration alkaline conditions remain scarce. Here, AEMWE is performed using an originally synthesized AEM and a self‐supported porous anode catalyst to systematically investigate the impact of ionomer layer thickness and uniformity on electrolysis performance. We further show that coating a thin layer of Ni nanoparticles onto the AEM improves contact at the membrane–catalyst layer interface. Membrane–electrode assemblies (MEAs) engineered to form suitable membrane–ionomer and ionomer–catalyst interfaces exhibit improved ionic conductivity and, consequently, enhanced performance in AEMWE with low‐concentration alkaline solution. This study highlights the importance of interfacial design in AEMWE and provides insight into the rational design of MEAs for efficient operation under diluted alkaline conditions.