Surface self-assembled multi-level NiFe-LDHs integrated super-hydrophilic diaphragms enabling efficient alkaline water electrolysis for high current density and durability

Abstract

Alkaline water electrolysis is one of the most potential techniques for green hydrogen production, offering high energy conversion and storage. High current density and durability of diaphragms are crucial for electrochemical performance. Here, we have developed a high-performance composite diaphragm based on in-situ self-assembly of nickel–iron layered double hydroxides (NiFe-LDHs) loaded on Zirfon-type substrate, and at the same time, catalytic NiFe-LDHs integrated the anode side for high-performance alkaline water electrolysis. By modulating the microstructure, a unique surficial feature with high surface free energy and super-hydrophilicity to address the issue of high ohmic resistance is established and achieves rapid OH−conduction and high catalytic oxygen evolution reaction (OER). Consequently, the prepared ZLDH-χ series diaphragm affords excellent application properties, with a ZLDH-10 diaphragm with an ultra-short wetting time of 0.23 s and a reduction of 120 mV over-voltage in a single electrolytic cell. Electrolyzer with ZLDH-10 diaphragm provides exceptional current density of 1400 mA cm−2 at 2.0 V in 80°C 30 wt% KOH. Importantly, a large-scale ZLDH-10 diaphragm with 37 × 37 cm2 can be readily made and reaches unprecedented durability at 1000 mA cm−2@1.8 V over 240 h. Both the simple in-situ self-assembly approach and excellent performance of the ZLDH-χ series diaphragm pave a new way for manufacturing diaphragms in advanced alkaline water electrolysis. A partial polarization method was first invented to figure out the contribution ratio for cell voltage reduction between NiFe-LDHs catalytic effect and hydrophilic improving effect.