在1-乙基-3 -甲基-咪唑氰胺離子液體中以電化學法製備多孔鎳電極並應用於製作氧化鈷擬電容器電極

Abstract

In this study, the 1-ethyl-3-methyl -imidazolium dicyanamide (EMI-DCA) ionic liquid for electrochemical application was evaluated with transition metal ion. The temperature dependency of the density and absolute viscosity of EMI-DCA were measured. Due to the ligand property of the DCA- anion, CuCl and NiCl2 are soluble in EMI-DCA. Amperometric titration experiments suggest that Ni(II) reacted with DCA- anions forming [Ni(DCA)4]2- complex anion, which could be reduced to metal via a single-step electron transfer process. Cyclic voltammograms of Ni(II), Cu(I), and Ni(II) + Cu(I), respectively, in EMI-DCA were recorded on the glassy carbon electrode. The thermodynamic deposition potentials of Ni and Cu are very close to each other and favorable for the electrodeposition of Ni-Cu alloys. The Ni-Cu alloys were electrodeposited using bulk controlled-potential electrolysis experiments. Energy-dispersive spectroscopy (EDS) data indicates that the composition of the Ni-Cu alloys not only depends on the deposition potential, but also on the Cu(I) and Ni(II) concentrations in the ionic liquid. The preparation of porous Ni films by electrochemical deposition of Ni-Cu alloy followed by the selective anodic etching of the active component (Cu) from the alloy was studied in the EMI-DCA ionic liquid containing Cu(I) and Ni(II) at room temperature. Afterwards, anodic deposition was carried out to disperse Co oxide onto the porous Ni substrate. As a result, a novel oxide electrode with a high-porosity structure was fabricated by the totally electrochemical procedure, which is very simple and efficient. Pseudocapacitive performance of this Co oxide electrode was evaluated by cyclic voltammetry in 1 M KOH solution. The data indicated that specific capacitance of the Co oxide was as high as 1356 F/g, which was 6-fold over that of flat Co oxide. Capacitance retained ratio after 500 charge–discharge cycles of the Mn oxide was also significantly improved from 75 % to 93 % due to the use of the porous substrate.