The electrochemical cycling and electrodeposition of lead from 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid

Abstract

The electrochemical behavior and deposition morphology of Pb2+ was investigated in the Room Temperature Ionic Liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide ([C2mim][NTf2]) containing the salt Pb(NTf2)2. Cyclic Voltammetry (CV) experiments were found to result in a range of electrochemical responses depending on the working electrode material being used, with both Pt and Pb based electrodes showing the highest current and lowest overpotential for deposition, respectively. Pb was found to undergo a single diffusion controlled reduction process at a coulombic efficiency of 95 % on a Pt working electrode. The deposition of Pb was found to follow a 3 dimensional progressive nucleation mechanism, regardless of the substrate material or the temperature during the experiment. During the deposition, the diffusion coefficient of Pb2+ was found to be 1.3×10−7cm2.s−1 by chronoamperometric analysis. Finally, the resulting morphologies of the Pb metal deposits were found to be heavily dependent on the deposition substrate, ranging from pyramids of 3μm in diameter on Pt, to fine sub-micron interwoven needles on glassy carbon. Interestingly, the potential of deposition appeared to make little difference to the resulting morphology on Cu substrates. Finally, to demonstrate the cycling ability of the Pb metal surfaces, Pb was cycled on Pb electrodes 200 times, showing that the resulting Pb films were compact and non-dendritic in nature. It is concluded that [C2mim][NTf2] containing Pb(NTf2)2 shows many favourable cycling characteristics.