High-Performance Composite Separator with a Porous Bicontinuous Structure for Alkaline Water Electrolysis.

Alkaline water electrolysis is considered an optimal technology for large-scale production of green hydrogen because of its economic and mature characteristics. The separator plays a crucial role in the alkaline water electrolysis process, as it fulfills the functions of gas separation and electrolyte transport. Nevertheless, the development of advanced separators with low ohmic resistance, high gas barrier ability, and good durability simultaneously remains a major challenge. Here, we first fabricated a series of high-performance composite separators with a porous bicontinuous structure by employing a nonsolvent-induced phase separation technique using a "weak solvent" (a solvent with a low affinity toward the membrane-forming polymer). The unique porous bicontinuous structure endows the membranes with high porosity, narrow pore size distribution with nanopores, and good hydrophilicity. As a result, the composite separator exhibits not only a low area resistance (0.13 Ω·cm) but also a high bubble point pressure (5.1 bar). The composite separator also displays excellent durability in both long-term electrolysis and alkaline-aging tests.