Voltammetric Study and Electrodeposition of Ni(II)/Fe(II) in the Ionic Liquid 1-Butyl-1-Methylpyrrolidinium Dicyanamide

Ionic liquid 1-butyl-1-methylpyrrolidinium dicyanamide (IL BMP-DCA) was used as the electrolyte to study the voltammetric behavior of Ni(II) and Fe(II) introduced into the IL as their chloride and sulfate salts. Compared with the aqueous system, the separation of reductive potential between the Ni(II) and Fe(II) was significantly decreased in this IL. The electrodeposition of Ni-Fe alloys was thus easily achieved using constant-potential electrolysis at copper substrate. No anomalous electrodeposition of Ni-Fe, which is common in aqueous system, was observed in this IL, resulting in the easy control of alloy compositions. The electronic spectra indicated that the coordinations of Ni(II) related to the precursors used in the IL, and the surface morphology of the Ni-Fe alloys was affected by the precursors as well as the electrodepositing potentials. Crystalline Ni and Ni-Fe were obtained from this system but crystalline Fe was only obtained at high temperature. The obtained Ni-Fe alloys were converted to the corresponding metal oxides/hydroxides via electrochemical oxidation in alkaline solution, and the linear scan voltammetric study indicated that these Ni-Fe alloys are potential substitutes for Pt as electrocatalysts of oxygen evolution reaction.