Fabrication And Properties Of Nanoporous Ni/NiO

Ni-based metallic glasses are selected for dealloying precursors in this thesis.By controlling the dealloying time in different concentration of HF etching solution, nanoporous Ni(np-Ni)includinga amorphous alloy interlayerare successfully fabricated by chemical dealloying at room temperature.Based on nanoporous nickel skeleton, nickel oxide(NiO) or nickel mixed oxides/hydroxides(NiO_x)aregenerated by natural oxidation, to form a sandwich structured np-Ni/NiO or np-Ni/NiO_x free-standing composite electrode materials. The main contents are included in this thesis are as following,Ni45Ti20Zr25Al10 is designed as the starting precursor alloys to synthesizecomposite electrode materials via free-dealloying in in different concentration of HF etching solution.The microstructure and the morphology together with elemental compositionof the sample before and after dealloyingwere examined by X-ray diffractometer(XRD) and a scanning electron microscope(SEM)respectively. The electrochemical performanceof composite electrode materials was evaluated by electrochemical workstation. The thesis aims at synthesizing free-standing compositeelectrode materialscould be directly used as a binder-free electrochemical supercapacitor electrode without the auxiliary components like conductive additives and binders.The morphology structure of electrode materials changes with varying thepreparation method and preparation technologies. A kind of electrode material possesses a sandwich structure, including doublenp-Ni/self-grown NiO nanorods nanocomposite films and a amorphous alloy interlayer after immersion in 0.5 M HF solution for 60 minutes. Another kind of material also possesses a sandwich structure, including doublenp-Ni/self-grown NiO_xnanocomposite films and a amorphous alloy interlayer after immersion in 0.05 M HF solution for 120 minutes. Dealloyingtime has a larger effect on the morphology of composite electrode materials, As the increase of the dealloyingtime, the morphology of composite electrode materials become more uniform. It is found that the np-Ni/NiO_x nanocompositewith nanoporous structure on surface exhibit much higher specific capacitane values of 847.9 F/cm3 at the scanning rate of 2.5 mV/s than the np-Ni/NiO nanocomposite with NiO nanorods on surface, indicating that the morphology of the electrode materials has important influence on electrochemical properties.The specific capacitances of the np-Ni/NiO and the np-Ni/NiO_xnanocompositedecreses 5.6% and 3.3%, which exhibits quite excellent cycling stability.