In this work, a hierarchical NiFe-LDH/Ni₃S₂@Ni-foam heterostructure was rationally constructed on conductive Ni foam via a two-step hydrothermal strategy and evaluated as an efficient oxygen evolution reaction (OER) electrocatalyst. Thiourea-assisted sulfurization of Ni foam produced vertically aligned Ni₃S₂ nanosheets, which served as a highly conductive and porous scaffold. Subsequent hydrothermal growth of NiFe layered double hydroxide (LDH) nanosheets on the Ni₃S₂ surface resulted in an intimately coupled NiFe-LDH/Ni₃S₂@Ni-foam nanoarchitecture. X-ray diffraction and FE-SEM analyses confirmed the successful formation of both Ni₃S₂ and NiFe-LDH phases and revealed a well-defined hierarchical nanosheet network. XPS further demonstrated the coexistence of Ni²⁺ and Fe³⁺ species and suggested strong interfacial electronic coupling between NiFe-LDH and Ni₃S₂. Benefiting from the synergistic combination of the conductive Ni₃S₂ backbone and the highly active NiFe-LDH nanosheets, the NiFe-LDH/Ni₃S₂@Ni-foam electrode exhibited superior OER performance, delivering overpotentials of 315 and 325 mV at 50 and 100 mA·cm^-2, respectively, along with a low Tafel slope of 72 mV·dec⁻¹, thereby outperforming both Ni₃S₂@Ni-foam and NiFe-LDH@Ni-foam. Electrochemical impedance spectroscopy and ECSA analysis further revealed reduced charge-transfer resistance and significantly increased active surface area for the heterostructured sample. This study provides a simple and effective strategy for designing high-performance OER electrocatalysts via interfacial engineering of sulfide and LDH nanostructures.

Keywords: Electrocatalysis, Oxygen evolution reaction, NiFe-LDH/Ni₃S₂@Ni-foam, Interfacial engineering, Hydrothermal synthesis