Single Nanometer-Sized NiFe-Layered Double Hydroxides as Anode Catalyst in Anion Exchange Membrane Water Electrolysis Cell with Energy Conversion Efficiency of 74.7% at 1.0 A cm–2

We used a liquid phase reaction to synthesize a nickel (Ni) and iron (Fe)-containing layered double hydroxide (NiFe-LDH), having a lateral size less than 10 nm. A chelating agent introduced into the media was thought to increase the concentration of metal hydroxide nuclei and suppress excessive growth of the LDH crystal, resulting in the synthesis of nanometer-sized LDH. The NiFe-LDH catalyzed the oxygen evolution reaction (OER) at an overpotential of 247 mV and current of 10 mA cm–2, which is superior to the performance of conventional iridium oxide (IrO x ) catalysts. Notably, a membrane electrode assembly (MEA) for anion exchange membrane water electrolysis using NiFe-LDH as an anode catalyst exhibited an energy conversion efficiency of 74.7% for flowing 1.0 A cm–2 in 1 M KOH at 80 °C. This efficiency is the highest among MEAs implemented with non-noble metal-based catalysts reported to date and offers a viable replacement for IrO x anode catalysts.