Porous PVA skin-covered thin Zirfon-type separator as a new approach boosting high-rate alkaline water electrolysis beyond 1000 hours’ lifespan

Regulating the pore structure of a zirfon-based diaphragm is critical to promoting a high-rate alkaline electrolyzer, but it is still a big challenge to respond "trade-off" between the thickness of the diaphragm and the current density/gas barrier behavior. In this work, a porous hydrophilic skin layer with ∼μm thick of polyvinyl alcohol (PVA) has been successfully constructed and casted onto the thin zirfon-type separator composite (V-Zirfon-350μm). The V-Zirfon-350 μm separator generates a high KOH uptake (>90%), low area resistance (0.2026 Ω cm2) but a low electrolyte permeation flux density (0.52 L cm−2 s−1 at 0.5 bar), which largely surpasses the state-of-the-art commercial Zirfon UTP-500 μm diaphragm. When coupled with Raney Ni cathode and NiCoMo-LDH anode catalysts, the V-Zirfon-350 μm separator offers a high current density over 1300 mA cm−2 @2.0 V (80 oC in 30% KOH) and a superior stability of 300 h under 800 mA cm−2 for alkaline water electrolysis (AWE). Specifically, the voltage is merely ∼3.5 V for two electrolytic cells connected in series, which can be even conducted for more than 1300 h at different operational conditions. This work provides a novel methodology for the practical application of a thin Zirfon-based diaphragm.