Investigation of electrochemical charge storage in nickel-cobalt-selenide/reduced graphene oxide composite electrode and its hybrid supercapacitor device

Nickel-cobalt chalcogenide-based composite materials were prepared by two-step hydrothermal technique. The change in morphology and crystalline phase of the materials with addition of 2D RGO sheet and exchange of anion by selenium was investigated. The alteration in electrochemical properties was also studied and correlated with the change in physicochemical properties. The electrochemical properties of the materials enhanced significantly when selenization occurred in presence of reduced graphene oxide (RGO) sheets. The NiCo2Se4/RGO (NCSG) electrode achieved highest specific capacitance of 1776 F g(-1) at 2 A g(-1) current density and retained excellent specific capacitance (51%) even at high (50 A g(-1)) current density. When the NCSG was integrated with sonochemically reduced graphene oxide (SRGO) and formed a hybrid supercapacitor (HSC) (SRGO//NCSG), the device delivered high specific capacitance of 212 F g(-1) at 2 A g(-1) current density. The HSC achieved a maximum energy density of 66.2 W h Kg(-1) at 1500 W kg(-1 )power density, which is comparable or higher than those of other ternary metal selenide supercapacitors. The HSC exhibited the retention in specific capacitance of -93.5% after 5000 GCD cycles, confirmed the good stability and reversibility. These results promoted the NCSG/RGO composite as a new type of promising supercapacitor electrode material. (C) 2020 Elsevier B.V. All rights reserved.