Highly Active and Durable FeNiCo Oxyhydroxide Oxygen Evolution Reaction Electrocatalysts Derived from Fluoride Precursors

Developing highly active and durable electro-catalysts, consisting of earth-abundant elements, for oxygen evolution reaction (OER) is pivotal for large-scale water splitting for hydrogen production. Herein, we report that the commercially available FeNiCo alloy can be converted to a highly active electrocatalyst for OER by galvanostatic anodizing in a fluoride-containing ethylene glycol electrolyte. Anodizing of the alloy develops a porous film consisting of the (FeNiCo)F-2 phase, which is readily converted to a highly active porous oxyhydroxide during anodic polarization in a KOH electrolyte. The anodized alloy exhibits high activity and high durability for OER with an overpotential as low as 0.26 V at a current density of 10 mA cm(-2). The present study demonstrates that a simple and cost-effective anodizing process can be used to form a highly active OER electrode from a low-cost, practical, iron-based alloy. In addition, we found that fluorides containing Fe, Ni, and Co are excellent precursors for the formation of oxyhydroxides exhibiting high OER activity and durability.