Porous PVA skin-covered thin Zirfon-type separator as a new approach boosting high-rate alkaline water electrolysis beyond 1000 hours’ lifespan
Xi Luo, Nengneng Xu, Yongnan Zhou, Xiaohui Yang, Woochul Yang, Guicheng Liu, Joong Kee Lee, Jinli Qiao
Abstract
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.