Design Strategy for an Efficient Bifunctional Electrocatalyst (IS-NiFeNC) for Overall and Solar-Cell Water Splitting

Herein, we demonstrated an interconnected nanospherical interconnected spherical (IS) NiFe-impregnated N-doped carbon (IS-NiFeNC) electrocatalyst prepared successfully by simple flame pyrolysis followed by a solvothermal method. IS-Ni6Fe4NC has a good morphology to have intimate contact with the electrolyte which significantly boosts the bifunctional activity in a harsh alkaline electrolyte (1.0 M KOH). The well-designed IS-Ni6Fe4NC/nickel foam (NF) nanosphere achieves a 10 mA/cm2 geometrical current density for the OER and HER with very low overpotentials (η) of 241 and 95 mV and small Tafel slopes of 83 and 95 mV dec–1, respectively. The higher electrochemical surface area (110 m2 g–1) and lower resistivity (2.8 Ω) of IS-Ni6Fe4NC easily exhibited kinetically sluggish electrode reactions. In a full-cell experiment, a nonprecious electrode couple of IS-Ni6Fe4NC/NF//IS-Ni6Fe4NC/NF required a lower cell voltage of 1.62 V to drive 10 mA cm–2 than the voltage required for bare NF//NF (1.87 V). The synergistic chemical coupling of NiFe with N-doped carbon improved the stability and assisted in generating active phases during the OER and HER processes, thus resulting in outstanding durability even after 200 h with an ∼3.4% potential loss. The solar-driven water electrolysis established the practical use of IS-Ni6Fe4NC/NF for eco-benign industrial H2 production. This work lays valuable experimental and postcharacterization foundations for the structure and properties of cost-effective bifunctional catalysts.