Preparation And Capacitive Performance Of NiMnO₃/Ni(OH)₂

In this paper,the NiMnO3 and NiMnO3/Ni(OH)2 are prepared by hydrothermal method.X-ray powder diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)are carried out to analyze the structures of NiMnO3 and NiMnO3/Ni(OH)2.The morphology of NiMnO3 and NiMnO3/Ni(OH)2 are observed by scanning electron microscope(SEM).It can be seen from SEM images that NiMnO3 possess irregular thin sheets structure and the NiMnO3/Ni(OH)2 possess flower-like structure composed of sheets.The cyclic voltammograms,chronopotentiometry and A.C.impedance are performed in order to evaluate the capacitive performance of NiMnO3 and NiMnO3/Ni(OH)2.The NiMnO3 sheets grown on multifunctional nickel foam is designed with manganese sulfate monohydrate(MnSO4·H2O)and foam nickel though a facile,ecofriendly and straightforward hydrothermal method,in which NF acts as substrate,reductant and Ni resource.The cyclic voltammograms,chronopotentiometry and A.C.impedance are carried out in order to analyze the capacitive performance of NiMnO3.The specific capacitance of NiMnO3 is 750 F g-1 in 1 M KOH and 1 M Na2SO4 mixed solution at current density of 1 mA cm-2.And it maintains 650 F g-1 at the current density of 10 mA cm-2,which is 87%retention.The cyclic stability of NiMnO3 is further researched at the current density of 10 mA cm-2,the specific capacitance is from 650 F g-1 to 541 F g-1,the capacitance retention is 83%after 2000 times of charging and discharging.In order to improve the capacitive performance of the material,nickel nitrate hexahydrate(Ni(NO3)2·6H2O)is added to the raw materials.The results indicate that the NiMnO3/Ni(OH)2 composite has superior capacitive performance when the mole ratio of Ni(NO3)2·6H2O and MnSO4·H2O is 2:1,the hydrothermal time is 10 h and the hydrothermal temperature is 180?.The specific capacitance of NiMnO3/Ni(OH)2 is 2722 F g-1 in 1 M KOH and 1 M Na2SO4 mixed solution at current density of 1 mA cm-2.The cyclic stability of NiMnO3/Ni(OH)2 is further researched at the current density of 10 mA cm-2,the specific capacitance is from 4194 F g-1 to 3397 F g-1,the capacitance retention is 81%.An asymmetric capacitor is assembled by using NiMnO3/Ni(OH)2 as positive electrode and RGO as negative electrode.The electrode offers the specific capacitance of 315 F g-1 at 1 mA cm-2 and maintains 262 F g-1 even at the current density of 10 mA cm-2 in 1 M KOH and 1M Na2SO4 mixed solution.At current density of 10 mA cm-2 after 2000 times of charging and discharging,the capacitance retention is 83%.The energy density and power density is 39.4 Wh Kg-1 and 1647.2 W Kg-1,respectively.