A Durable and Hydrophilic Separator with Multiscale Cross-Linking for Long-Term Alkaline Water Electrolysis

A separator plays a critical role in alkaline water electrolysis (AWE or ALK) for high-efficiency hydrogen production. Traditional polyphenylene sulfide (PPS) separators suffer from the challenges of poor hydrophilicity, high internal resistance, and limited durability. Herein, a durable and hydrophilic PPS separator with a modified multiscale cross-linking coating layer is proposed. The coating layer is constructed through sequential codeposition of polydopamine/polyethylenimine, followed by interfacial polymerization involving modified ZrO2 nanoparticles, PEI, and cyanuric chloride to create a robust organic–inorganic hybrid network with covalent cross-linking. The resulting separator exhibits a low area resistance (0.13 Ω cm–2), and the electrolyzer achieves a high current density of 0.8 A cm–2 at 2.05 V under 75 °C, arising from the enhancement of the separator’s hydrophilicity due to polar groups and hydrophilic ZrO2 within the coating layer. The electrolyzer stability tests further confirm a stable voltage and minimal resistance increase over time, attributed to the synergistic effects of covalent cross-linking and ZrO2 reinforcement, which enhance separators’ structural integrity and alkaline resistance. This study thus offers a scalable approach to designing high-performance ALK separators, with enhanced durability, enabling sustained hydrogen production under industrial conditions.