An underlying nickel difluoride material as bifunctional electrode for energy storage and hydrogen evolution reaction

Abstract

Supercapacitors (SC) with high power density and long cycle life and hydrogen evolution reactions (HER) with green and environment-friendly act a significant role in the field of electrochemical storage and conversion. It is very important to develop low-cost and high-performance positive materials and hydrogen evolution catalysts for the application of SCs and HER devices. At the same time, it is very significant to develop multifunctional electrode materials that can be used for both energy storage and energy conversion devices. Nickel-based materials are widely used in the field of SCs because of their high specific capacitance and abundant reserves. In addition, the transition metal nickel element is located near the top of the volcanic curve, that is, nickel-based materials have obvious advantages as hydrogen evolution catalysts. Therefore, it is of great significance to develop nickel-based bifunctional electrode materials. In this work, NiF2 material with rutile phase structure was prepared by a simple solvothermal method. Electrochemical tests in different electrolytes of three-electrode system show that NiF2 has electrochemical activity only in alkaline electrolyte. Surprisingly, the bifunctional electrode material NiF2 has an excellent specific capacitance of 889.2F/g at 0.5 A/g in 6 M KOH electrolyte. Even at 10 A/g, the specific capacitance remains at 617.1F/g, and the retention rate is 69.8 %, which has excellent rate performance. At the same time, the capacity retention rate is 80 % after 10,000 cycles. Furthermore, the HER based on NiF2 electrode shows that 10 mA cm−2 can be reached at an overpotential of 176 mV, and the Tafel slope is 125 mV dec−1 in 1 M KOH, which has excellent cycle stability. Therefore, its excellent electrochemical performance indicates that NiF2 will be a very hopeful electrode material in the future in fields of SC and HER.