Scalable fabrication of high-performance asymmetric hierarchical porous membranes for alkaline water electrolysis

Alkaline water electrolysis (AWE) represents a promising approach for green hydrogen production, yet the development of high-performance separators with gas impermeability, high ion conductivity, and stability under alkaline operating conditions has proven challenging. To address this challenge, we develop a pre-concentration regulated phase separation strategy for scalable fabrication of asymmetric hierarchical porous membranes (AHPMs) for AWE. The resulting AHPMs demonstrate a hierarchical structure composed of an ultrathin dense skin layer and highly interconnected porous support. Benefitting from the structural advantages, the AHPMs exhibit outstanding characteristics, including a high bubble point pressure up to 12.4 bar, extremely low area resistance of 0.03 Ω cm2 in 30 wt% KOH at 80 °C, and excellent hydrophilicity and long-term alkaline stability. When applied in AWE with commercial catalysts, the AHPMs achieved an impressive current density of 1.9 A cm−2 at 2.0 V in 30 wt% KOH and the anodic hydrogen contents (AHCs) below 0.5 vol.% at a low current density of 0.1 A cm−2, differential pressure of 2 bar, and temperature of 80 ℃. Moreover, AHPMs demonstrate exceptional stability over 2,400 h of continuous operation and maintain superior performance in a 1 Nm3 h−1 industrial-scale electrolyzer stack. This work advances the development of efficient separators for high-performance AWE systems, contributing to the advancement of hydrogen technologies in sustainable energy applications.