Morphology control plays a pivotal role in achieving an exceptionally efficient electrocatalyst with abundant active sites and outstanding electrical conductivity. In this study, we employed a sophisticated chemical nanoengineering technique to fabricate an exquisitely thin NiFe(OH) x electrocatalyst on Ni 3 S 2 nanosheets. Firstly, the Ni 3 S 2 nanosheets were synthesized through an innovative in situ one-step sulfurization reaction of the Ni(OH) 2 nanosheets grown on Ni foam. Subsequently, a remarkable ultrathin layer of NiFe(OH) x was precisely deposited onto the surface of the Ni 3 S 2 to form a captivating core-shell structure using a chemical dipping method. The resulting electrode, denoted as NiFe(OH) x /Ni 3 S 2 /NF, exhibited exceptional electrocatalytic activity and durability towards the oxygen evolution reaction (OER), owing to its expansive specific surface area, rapid electron transport, and robust interlayer bonding. Notably, this electrode achieved an impressive current density of 100 mA cm -2 at an astonishingly low overpotential of 218 mV while maintaining a low Tafel slope of 37.9 mV dec -1 and remarkable stability for up to 12 days in 1 M KOH aqueous solution. This work presents an alluring novel approach for constructing highly efficient ultrathin catalysts for water splitting.