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. Ni-Fe alloys are important materials that have been investigated for multiple applications including magnetic materials, 1-4 electrochemical multivalent memory, 5 and highly active electrocatalysts of oxygen evolution reaction (OER). [6][7][8][9][10][11][12][13][14][15] Recently, Ni-Fe alloys have attracted much attention because OER is crucial to energy storage/conversion such as rechargeable metal-air batteries and electrochemical watersplitting. For the latter one, the potentials of both electrodes always determine the cell voltage. The OER is usually the rate determining step and contributes more significantly to the amount of potential required beyond the theoretical cell voltage. The cell voltage can be efficiently decreased by using an efficient electrocatalyst as the anode to reduce the overvoltage of OER, but precious metal-containing electrocatalysts should be avoided because of their high cost. Ni-Fe alloys, therefore, show their advantages to be OER electrocatalysts. Ni-Fe alloys are also used for hydrogen evolution reaction (HER) 16 and for the electrodetection of an important organic molecule, 4-aminophenol. 17 Electrodeposition is widely utilized to prepare metal alloys, including Ni-Fe alloys. 3,4,[18][19][20][21][22] Although Ni-Fe alloys can be prepared using various techniques such as sputtering and ball milling, electrodeposition may be the most feasible for low-cost mass production. The electrodeposition of Ni-Fe alloys from aqueous baths, therefore, have been widely studied, 3,4,[18][19][20][21][22] 20 can be easily prepared using electrodeposition. The electroplating baths of Ni-Fe alloys are composed of simple salts with or without complexing agents. The complexing agent-containing baths are more stable, especially at high pH.28-30 However...

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