A thin and flexible composite membrane with low area resistance and high bubble point pressure for advanced alkaline water electrolysis

Green hydrogen plays a pivotal role in the decarbonizing process. Hydrogen production by alkaline water electrolysis (AWE) is the most promising way for large-scale hydrogen production because of the merits of high-efficient and cost-effective. In the AWE system, the membrane is used to conduct hydroxide ions and block the interpenetration of hydrogen and oxygen, which is a crucial component. However, the current membranes are limited by either the high area resistance or inadequate gas-blocking ability. Herein, we proposed a thin (∼268 μm) and flexible composite membrane featuring both low area resistance (∼0.14 Ω cm 2 in 30 wt% KOH solution) and high bubble point pressure (BPP, ∼24 bar). When applied in alkaline water electrolysis, the composite membrane with the commercial NiMo and NiFe catalysts shows a current density of 2.3 A cm -2 at the voltage of 2 V in 30 wt% KOH solution at 80 °C, surpassing the capabilities of the ZIRFON UTP 500 membrane. Notably, the in-situ gas purity tests reveal an impressive hydrogen purity of ∼99.997%, much higher than that of the state-of-the-art membranes. Additionally, the stability tests conducted more that 600 h at 80 °C without performance attenuation highlight the membrane's competitiveness and promising commercial prospects.