Electrochemical reactions of Ni(II)/Ni and Fe(II)/Fe were investigated in a hydrophobic room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing Ni(TFSA)2 and Fe(TFSA)2. The optimal conformation of high-spin metal ion (M(II) = Fe(II) and Ni(II)) with three trans-TFSA-were obtained using the theoretical calculations. The bigger molecular volume of Fe(II) species in BMPTFSA may lead to a smaller reduction peak current. The cyclic voltammetric results showed that the cathodic peaks of Ni(II) and Fe(II) emerged into one wave, which is close to the cathodic waves of individual metals and favorable for the co-electrodeposition of Ni-Fe. A non-anomalous codeposition behavior was found from BMPTFSA with Ni(TFSA)2 and Fe(TFSA)2. Ni-Fe deposits with different morphology and composition were obtained at various applied potentials and metal ion concentrations.
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