The interstitial composite separators constructed by flat-engineering for high-efficiency alkaline water electrolysis

Composite separators are widely used in alkaline water electrolysis due to their superior corrosion resistance. Herein, we obtained a series of separators with enhanced hydrophilicity, including a denser and smoother surface, by introducing additives and a heating treatment during the pre-evaporation process. Specifically, the interstitial strategy can be employed to address the issue of inadequate structural stability induced by conventional hydrophilic additives, such as polyvinylpyrrolidone, by utilizing TiO₂ with hydrophilicity and particle size differences from ZrO₂. This approach optimizes the hydrophilicity and pore size distribution, while enhancing the ductility. Z₈T₂ exhibits superior overall performance with an area resistance of merely 0.103 ​Ω·cm², substantially outperforming the commercial Zirfon UTP500 (0.3 ​Ω·cm²). Using Raney Ni and NiFe-LDH as catalysts, the electrolyzer achieves a current density of 1401 ​mA/cm² at 1.9 ​V, demonstrating a significant improvement comparing with commercial Zirfon UTP500 (1053 ​mA/cm²). The separator exhibits remarkable stability at a current density of 400 ​mA/cm² for 300 ​h in 30 ​wt% KOH solution at 80°C and is also reused. This work provides a simple and universal strategy for process operation and additive control.