Electrodeposition of Lead from 1-butyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)amide Ionic Liquid

Abstract

The electrochemical behavior of lead (Pb) was investigated in an amide-type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA), containing Pb(TFSA)2. The cathodic and anodic currents corresponding to electrodeposition and stripping of Pb, respectively, were observed by cyclic voltammetry. The formal potential of Pb(II)/Pb couple was found to be −0.68 V vs. Ag/Ag(I), which is more negative by 0.11 V than that of Sn(II)/Sn couple. The diffusion coefficient of Pb(II) at 25°C was 0.8 × 10−7 cm2 s−1, which was close to those of divalent metal species in BMPTFSA. The local change of the viscosity and density of the ionic liquid near the electrode surface during electrodeposition and stripping of Pb was confirmed by electrochemical quartz crystal microbalance. The nucleation process and the morphology of electrodeposited Pb were found to be dependent on the deposition potential, probably due to accumulation of BMP+ at the surface of the negatively polarized electrode.