Vertically stacked bilayer heterostructure CoFe2O4@Ni3S2 on a 3D nickel foam as a high-performance electrocatalyst for the oxygen evolution reaction

Cobaltite systems with spinel-type structures and Ni-based sulfides are deemed to be practical and promising water oxidation electrocatalysts because of their low cost, intrinsically admirable electroconductivity and predominant durability. However, most electrocatalysts still suffer from the challenge of an increase in the loading of active materials without sacrificing the geometry area. In this work, a CoFe2O4@Ni3S2/NF composite was achieved through a series of hydrothermal and annealing processes by means of constructing a vertically stacked bilayer heterostructure CoFe2O4@Ni3S2 on a 3D porous nickel foam (NF). The structure and morphology of the as-synthesized catalyst have been characterized by powder X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis. The as-obtained CoFe2O4@Ni3S2/NF electrode, which possesses a vertically stacked bilayer nanosheet heterostructure, displays an improved OER performance and cyclic stability and shows an early onset potential with a low overpotential (231 mV at 10 mA cm−2) in a 1.0 M KOH solution. In addition, CoFe2O4@Ni3S2/NF demonstrates dependable durability and delivers outstanding current density of ∼15 mA cm−2 without activity degradation for 20 h. This approach provides a new insight into developing earth-abundant, low-cost and high-efficiency OER electrocatalysts.