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 (IrOx) 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 IrOx anode catalysts.