In-situ synthesis of free-standing FeNi-oxyhydroxide nanosheets as a highly efficient electrocatalyst for water oxidation

The design and synthesis of efficient and affordable electrocatalysts for water oxidation are essential to advance water splitting technology, which depends on developing earth-abundant catalytic materials with rational compositions and structures. Here, we propose a facile synthesis of FeNiOOH nanosheets grown on FeNi foam (FNF) by in-situ chemical oxidation as a novel 3D electrode for oxygen evolution reaction (OER). This FeNiOOH/FNF electrode shows outstanding electrocatalytic performance in alkaline electrolyte, including high OER activity that requires a small overpotential of 252 mV to achieve a current density of 10 mA cm, favourable OER kinetics with a low Tafel slope of 36.8 mV dec, and excellent operation stability for at least 50 h. The superior OER properties are resulted from the highly active FeNi-oxyhydroxide species and advantageous nanosheet array structure. This work presents an effective strategy to rationalize self-supporting electrodes consisting of nanostructured arrays on conductive substrates, creating new opportunities to search for more advanced materials towards a sustainable energy future.