Hierarchical FeOOH@NiCo2S4 Core-Shell Heterostructure Supported on Nickel Foam as an Efficient Electrocatalyst for Oxygen Evolution Reaction

Amorphous FeOOH nanosheets were electrodeposited onto nickel foam (NF)-supported NiCo2S4 nanotube arrays to form a three-dimensional FeOOH@NiCo2S4/NF core-shell heterostructure, which is a bifunctional electrocatalyst for overall water splitting (OWS). FeOOH@NiCo2S4/NF pre-catalyst showed a good electrocatalytic activity and stability for the oxygen evolution reaction in a 1 M KOH solution, with an overpotential of 228 mV at 10 mA cm(-2), a Tafel slope of 44.03 mV dec(-1) and a durability of more than 50 h. The overpotential of the hydrogen evolution reaction was 112 mV at 10 mA cm(-2). The OWS performance was very good because it only required a voltage of 1.56 V at 10 mA cm(-2). The 3D core-shell structure with a large electrolyte contact interface, the good electronic conductivity, the large surface exposure of active sites by the NiCo2S4 nanotube arrays, and the strong electron interaction at the heterogeneous interface between FeOOH and NiCo2S4 are the key factors for the excellent performance.