Preparation And Capacitive Performance Of RGo/NiCo₂O₄/NiFe₂O₄ Hollow Nanospheres Composite Materials

In this paper,NiCo2O4/NiFe2O4 hollow nanospheres were prepared by a novel one-pot method.The structure of the composite was characterized by X-ray powder diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).The morphologies of the products were observed through transmission electron microscopy(TEM)and scanning electron microscopy(SEM).In addition,the electrochemical properties of NiCo2O4/NiFe2O4 and rGo/NiCo2O4/NiFe2O4 hollow nanospheres were investigated by cyclic voltammograms(CV),galvanostatic charge-discharge(GCD)and electrochemical impedance spectroscopy(EIS).We develop a novel one-step synthetic technology toward large-scale to construct the highly homogeneous NiCo2O4 hollow nanospheres(NSs),and introduced NiFe2O4 for the first time.The NiCo2O4/NiFe2O4 achieves real nanoscale.In addition,the electrochemical performances are increased amazingly compared with NiCo2O4.Importantly,the ratio of NiFe2O4 plays important role for the improvement of electrochemical performance.The NiCo2O4/NiFe2O4 hollow nanospheres have excellent specific capacitance values.In the 6 M KOH,The NiCo2O4/NiFe2O4 hollow NSs exhibit superior capacitance values(3795 F g-1 at a current density of 1 A g-1)and fine cycling performances(11.0%specific capacitance decay after 6000 cycles),Such outstanding electrochemical performance is deemed to be ascribed to the real nanosized hollow structure with the porous shell,well-pleasing uniformity,high surface area and synthesic effect of each component.Graphite was used as raw material,and the improved Hummers method was used to obtain reduced graphene oxide.The composite of rGo/NiCo2O4/NiFe2O4 was prepared by electrochemical deposition.By controlling the single factor variable analysis method,the optimal conditions and excellent specific capacitance of the rGo/NiCo2O4/NiFe2O4 were obtained.When the current density is 1 A g-1,the specific capacitance of the composite can reach 3926 F g-1 under the potential window of 0-0.5 V,and the specific capacitance retains 93.9%of the initial value after 6000 cycles.The composite of rGo/NiCo2O4/NiFe2O4 was used as the cathode and graphene was used as the anode.The rGo/N iCo2O4/N i Fe2C4 asymmetric supercapacitor was assembled.The energy density and power density of the asymmetric capacitor were 36.5 Wh kg-1 and 1510 W kg-1 respectively.