Reverse Microemulsion‐Assisted Synthesis of NiCo2S4 Nanoflakes Supported on Nickel Foam for Electrochemical Overall Water Splitting

Abstract Developing low‐cost and highly efficient bifunctional electrocatalysts for the hydrogen evolution reaction and the oxygen evolution reaction has been the subject of intensive research focus with the increasing demand for energy conversion technologies. Herein, synthesis of nickel cobalt sulfide (NiCo2S4) nanoflakes grown on 3D nickel foam (NF) is reported by a reverse microemulsion‐assisted method appearing benign water‐splitting activity and stability. The binder‐free, self‐supported NiCo2S4/NF electrode delivers a current density of 100 mA cm–2 at an overpotential of 319 mV for the oxygen evolution reaction and a current density of 10 mA cm–2 at 169 mV for the hydrogen evolution reaction in 1 m KOH. When using it as a cathode and an anode in a two‐electrode water electrolysis system, it demonstrates a remarkable activity for overall water splitting to deliver 10 mA cm–2 at a cell voltage of 1.61 V, thus offering an attractive cost‐effective earth abundant electrocatalyst toward water splitting.