Electrodeposition of lead on glassy carbon and mercury film electrodes from a distillable room temperature ionic liquid, DIMCARB

The electrochemical reduction of Pb2+ has been studied in the ‘distillable’ ionic liquid DIMCARB (a mixture of adducts of dimethylamine and carbon dioxide, comprising both neutral and ionic moieties). Voltammetric results show that Pb2+ is reduced in a single step to form Pb metal via a nucleation and growth mechanism on a glassy carbon electrode. Ex situ powder X-ray diffraction studies on deposited lead show the presence of both α- and β-PbO2, as well as elemental lead, suggesting the finely deposited lead particles are in an active rather than passive state. Chronamperometric and scanning electron microscope measurements show that the nucleation and growth follows a progressive nucleation mechanism on glassy carbon. Large peak–peak separations for the Pb reduction and oxidation are consistent with this mechanism and do not suggest electrochemical reversibility. However, experiments with co-deposition of Hg show that this irreversibility is a result of deposition onto a solid glassy carbon surface rather than a solvent effect. The diffusion coefficient of Pb2+ in DIMCARB has been calculated to be 1.8±0.4×10−7 cm2 s−1.