Uniform nanoporous zirconia composite membrane enabling high-performance alkaline water electrolysis

Zirconia-based membranes typically face a trade-off between ionic transport and gas barrier performance, limiting their effectiveness in alkaline water electrolysis, where low area resistance, high bubble-point pressure, and long-term stability are essential. Here we show a method for fabricating a nanoporous composite membrane. Yttria-stabilized zirconia nanoparticles are uniformly dispersed into a sol-state polybenzimidazole matrix via a one-pot sol-gel process. The resulting membrane exhibits a sponge-like, uniform nanoporous morphology with a high porosity of ~85%. Yet, it maintains a higher bubble-point pressure (>25 bar). Strong interfacial interactions exist between yttria-stabilized zirconia nanoparticles, phosphoric acid, and polybenzimidazole molecular chains. The synergistic multi-pathway structure facilitates continuous hydroxide ion migration. In alkaline water electrolysis, the membrane delivers a high current density of 13.1 A cm^-2 at 2.0 V, and operates effectively over a wide range of alkaline electrolyte concentrations. Reinforcement with a polyphenylene sulfide mesh enables stable operation for 7000 h, and the membrane performs reliably in a large-area single-cell stack. This work introduces a scalable route to gel-state ceramic-polymer membranes for high-efficiency hydrogen production.