Electrochemical Codeposition of Sm and Co in a Dicyanamide Ionic Liquid

Electrochemical deposition of lanthanides and their alloys can be implemented at room temperature from organic ionic media, such as ionic liquids (ILs). In this work, we studied Sm and Co electrodeposition and their codeposition in the [BMP][DCA] (1-butyl-1-methylpyrrolidinium) IL with controlled water content by electrochemical methods combined with scanning probe microscopy and X-ray analysis of the formed deposits. It is shown that both Co and Sm can be deposited electrochemically from the corresponding single–component solutions in the chosen IL and their deposition potential shifts positively at an increase in the water concentration (deposition acceleration). Sm–Co codeposition is observed in an IL solution containing ions of the both metals (Sm(III) and Co(II)). Here, Sm is codeposited at much less negative potentials (by 0.42 V) than those of Sm deposition from an IL solution containing only Sm(III) ions. An increase in the water concentration in the solution, however, results in inhibition of Sm–Co codeposition. We relate the inhibition of Sm–Co codeposition in the presence of water to formation of an oxide film on the deposit surface, which hinders further reduction of Co ions and therefore codeposition of Sm–Co.