Optimized Ion‐Transport Properties of Diallylammonium‐Cyclopolymerized Anion‐Exchange Membranes for High‐Performance Water Electrolysis

Abstract Anion‐exchange membranes (AEMs) are the key components of AEM‐based water electrolysis (AEMWE) for green hydrogen production. Unfortunately, many AEMs have unsatisfactory ion conductivity, and the factors governing their ion transport remain unclear. To address these limitations, herein, a new pyrrolidinium‐containing diallylammonium‐cyclopolymerized (PDT) AEM is proposed. Cyclopolymerization between diallyldimethylammonium chloride and tetraallylammonium bromide (TAAB, crosslinker) monomers in a porous polytetrafluoroethylene support yielded a pore‐filled crosslinked PDT membrane, whose structure is controlled by adjusting its TAAB content. The OH ⁻ conductivity of the PDT membrane is more strongly correlated with its OH ⁻ diffusivity (determined by its internal water content) than its OH ⁻ partitioning (determined by its internal charge content). The optimized PDT membrane exhibited low gas crossover and high thermomechanical stability. Importantly, it displayed excellent AEMWE performance in both pure water (0.71 A cm ⁻² at 1.8 V) and 1 m KOH (5.25 A cm ⁻² at 1.8 V) at 80 °C with half‐platinum‐group metal electrodes, outperforming many previously reported and commercial AEMs, owing to its significantly high OH ⁻ conductivity. The PDT membrane also demonstrated stable AEMWE performance in 1 m KOH at 60 °C for 300 h. This study offers an effective means to fabricate high‐performance AEMs and sheds light on their ion‐transport mechanisms.