Efficient oxygen evolution reaction (OER) electrocatalysts can accelerate the reaction kinetics of water-splitting for large-scale hydrogen generation. In this work, 2D nanosheets decorated with a 3D porous nanostructure, including Fe, Co and Ni elements, are developed via anodic cyclic voltammetry scanning (ACVs) in the presence of sodium sulfide (FeCoNi-NS-ACVs). The formed 2D nanosheets provide metal ions during ACVs to generate a 3D porous structure and also construct a hierarchical morphology to favor the transport of the electrolyte and release of produced gas bubbles. What's more, the developed FeCoNi-NS-ACVs possesses superhydrophilic and excellent electroconductivity properties. Benefiting from the above merits, FeCoNi-NS-ACVs exhibits excellent electrocatalytic performances for the OER with low overpotentials of 170 mV and 198 mV to drive 50 mA cm-2 and 100 mA cm-2, respectively, with a small Tafel slope of 64 mV dec-1 and remarkable durability over 50 h. Moreover, the FeCoNi-NS-ACVs also exhibits outstanding electrocatalytic activity and stability toward overall water-splitting.