Imidazole-Tailored Ionomers Achieve Concurrent Proton Conduction Boost and Electron Transport Retention in the Anode Catalyst Layer for PEM Water Electrolysis

In the anode catalyst layer (ACL) of proton exchange membrane water electrolysis, the ionomer confinement effect and its interfacial interactions with the IrO2 catalyst significantly impair proton transfer efficiency and catalyst utilization. This study develops an imidazole-doped ionomer through in situ polymerization to address these limitations. Imidazole is anchored within the ionomer nanochannels via acid–base coordination with sulfonic acid groups, forming hydration-assisted proton highways through hydrogen-bonding networks between imidazole nitrogen atoms and water molecules. Simultaneously, the coordinated imidazole suppresses ionomer adsorption on the IrO2 catalyst surfaces, reducing the number of poisoned Ir active sites and enhancing the electronic conduction between catalyst aggregates. The in situ polymerization strategy effectively prevents imidazole leaching, ensuring long-term operational stability. Compared to the traditional ACL, the modified membrane electrode assembly achieves significant improvement in water electrolysis performance by 14.2% (3.0 A cm–2@1.90 V) and exhibits exceptional durability (a 10.6 μV h–1 voltage decay rate for 1500 h). This approach provides an effective strategy for designing high-performance ionomer-catalyst interfaces in electrochemical energy systems.