Nickel-iron selenide polyhedral nanocrystal with optimized surface morphology as a high-performance bifunctional electrocatalyst for overall water splitting

Constructing earth-abundant and efficient electrocatalysts for overall water splitting are still in the research and exploration stage. In this work, the Fe-doped NiSe 2 polyhedron nanocrystals grown on Ni foam (Ni 0.75 Fe 0.25 Se 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. NiSe 2 is originally a catalytic active substance, and the Fe doping in NiSe 2 can greatly enhance the conductivity. The optimized Ni 0.75 Fe 0.25 Se 2 @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 Ni 0.75 Fe 0.25 Se 2 @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 RuO 2 (+)//Pt/C(−) couple) and excellent long-term stability of 50 h for overall water electrolysis.