A Chalcogenide-Derived NiFe₂O₄ as Highly Efficient and Stable Anode for Anion Exchange Membrane Water Electrolysis

Developing low-cost, highly active, and durable oxygen evolution reaction (OER) electrodes is one of the critical scientific issues for anion exchange membrane water electrolyzer (AEM-WE). Herein, we report a vacancy-rich and alkali-stable NiFe₂O₄-type electrode (named as NiFeO_x-350-O_v), derived from the chemical-vapor deposited precursor NiFeSe_xS_y-350, as an efficient and robust anode material. The obtained electrode affords current densities of 100 and 500 mA cm^-2 at overpotentials of 245 and 270 mV, respectively, and displays excellent long-term durability sustaining 1.0 A cm^-2 at least for 1000 h. When coupled with Ni₄Mo/MoO₂/NF as a hydrogen evolution reaction (HER) catalyst, the resulting platinum-group metal (PGM)-free single-cell AEM-WE exhibits a cell voltage of 1.71 V at the current density of 1000 mA cm^-2 at 80 °C and long-term durability during a current-cycling test between 0.5 A cm^-2 and 1.0 A cm^-2 over 150 h at 60 °C. This work highlights a unique reconstruction strategy for preparing highly active and durable OER catalysts used in PGM-free AEM-WE.