Electrochemical behavior of Ni(Ⅱ) in different ionic liquids

Abstract: The electrochemical behaviors of Ni(Ⅱ) with the addition of NiCl₂ to a 1-butyl-3-methylimidazolium chloride-glycerine (BMIC-GL) ionic liquid and a 1-butyl-3-methylimidazolium dicyanamide (BMIMDCA) ionic liquid were studied. Voltammetry analysis showed that the reduction potential of Ni(Ⅱ) in BMIMDCA-NiCl₂ ionic liquids was more positive than that in the BMIC-GL-NiCl₂ ionic liquid, indicating that the reduction of Ni(Ⅱ) in BMIMDCA-NiCl₂ was easier. In addition, the reduction reaction of Ni(Ⅱ) in both ionic liquids was a quasi-reversible process controlled by diffusion, but the diffusion coefficient in BMIC-GL-NiCl₂ was 8.92×10^-7 cm²/s, which was significantly greater than that in BMIMDCA-NiCl₂ (2.94×10^-7 cm²/s). Current-time transient analysis showed that the electrodeposition of nickel on a glassy carbon electrode in BMIC-GL-NiCl₂ ionic liquid followed the three-dimensional instantaneous nucleation mechanism, while that in BMIMDCA-NiCl₂ conformed to the three-dimensional progressive nucleation mechanism.