Electrochemistry of Manganese in the Hydrophilic N-Butyl-N-methylpyrrolidinium Dicyanamide Room-Temperature Ionic Liquid

Abstract

The electrochemistry of manganese was studied at a polycrystalline platinum disk electrode in the hydrophilic ionic liquid -butyl--methylpyrrolidinium dicyanamide (BMP-DCA). The density and absolute viscosity of BMP-DCA were determined over a temperature range from 299.0 to 343.0 K. A polynomial equation describing the temperature dependence of the density is provided. The viscosity obeys the Arrhenius temperature dependence. The dicyanamide anion exhibits a good complexing ability toward transition metal ions, and, therefore, Mn(II) species can be introduced into the ionic liquid either by anodic dissolution of a manganese electrode or by dissolution of manganese (II) chloride. Cyclic voltammograms indicated that the electrodeposition of Mn from Mn(II) was preceded by an overpotential-driven nucleation process. When the potential scan was reversed, the anodic stripping wave was fairly smaller than the cathodic wave, indicating that the oxidation of the Mn electrodeposits was kinetically hindered. However, this behavior was less noticeable for massive Mn electrodeposits. Manganese coatings were prepared at copper substrates by controlled-potential electrodeposition and characterized by scanning electron microscope, energy-dispersive spectrometer (EDS), and powder X-ray diffraction spectrometer (XRD). EDS analysis indicated that the purity of the Mn electrodeposits was good, although no crystal signal of Mn was observed in the XRD patterns.