Constructing earth-abundant and efficient electrocatalysts for overall water splitting are still in the research and exploration stage. In this work, the Fe-doped NiSe2 polyhedron nanocrystals grown on Ni foam (Ni0.75Fe0.Se-25(2)@NF) with controllable surface morphology are developed as high-performance bifunctional electrocatalysts. The surfaces of the optimized polyhedron nanocrystals provide high density of catalytic active sites. NiSe2 is originally a catalytic active substance, and the Fe doping in NiSe2 can greatly enhance the conductivity. The optimized Ni0.75Fe0.25Se2@NF (6 h) electrode are performed in an alkaline solution, exhibiting outstanding OER and HER activity with small overpotentials of 210 mV and-117 mV to reach current density of 10 mA cm(-2) and -10 mA cm(-2), respectively. Remarkably, the Ni0.75Fe0.25Se2@NF (6 h) electrode serve as cathode and anode in water splitting electrolyzer also demonstrates highly efficient overall water electrolysis performance, with a relatively low cell voltage of 1.61 V at 10 mA cm(-2) (1.57 V for RuO2(+)//Pt/C(-) couple) and excellent long-term stability of 50 h for overall water electrolysis.