Regulation of the morphology and electrochemical properties of Ni0.85Se via Fe doping for overall water splitting and supercapacitors

Abstract

An Fe-doped Ni_0.85Se nanosheets array on Ni foam was synthesized successfully through a one-step solvothermal method as an effective binder-free multifunctional catalyst for the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), overall water splitting and supercapacitors. As an electrocatalyst, the 0.8%Fe–Ni_0.85Se nanosheets array only required a small overpotential of 120 mV and a Tafel slope of 34.11 mV dec⁻¹ to deliver a current density of 10 mA cm⁻² for the HER. The 2%Fe–Ni_0.85Se nanosheets array can provide a large current density of 100 mA cm⁻² at an overpotential of 1.54 V and a Tafel slope of 73.40 mV dec⁻¹ for the OER. The 2%Fe–Ni_0.85Se(+)‖0.8%Fe–Ni_0.85Se(−) electrolyzer only needed a low cell potential of 1.52 V to reach 100 mA cm⁻² in 1.0 M KOH and exhibited long-term stability for 40 h. The remarkable HER, OER and overall water splitting properties of the Fe-doped Ni_0.85Se nanosheets array mainly originated from the unique nanosheets array morphology, high electronic conductivity, and large effective electrochemical active surface induced by Fe doping. In addition, the 2%Fe–Ni_0.85Se nanosheets showed supercapacitive properties, with a maximum specific capacitance of 1103.5 F g⁻¹ at a current density of 1 A g⁻¹, good cycling stability with a capacitance retention of 82% after 1000 cycles and a low charge transfer resistance of 0.0092 Ω.