Electrochemical Behavior of Pb(II) in NaCl–KCl Molten Salts

Abstract

The electrochemical behavior of PbCl₂ in NaCl–KCl molten salt on graphite and molybdenum electrodes was investigated using cyclic voltammetry, square wave voltammetry, chronopotentiometry, and open circuit chronopotentiometry at 750°C. A pair of redox peaks for Pb(II)/Pb was observed from the cyclic voltammetry (CV) results, with cathodic peak potentials of –0.16 and –0.2 V at the molybdenum and graphite electrodes, respectively. It was also confirmed that the reduction of Pb(II)/Pb was a one-step reduction process with a two-electron transfer and a quasi-reversible process. Square wave voltammetry (SWV) was also used to confirm the accuracy of the CV results further. The diffusion coefficients of Pb(II) ions on molybdenum and graphite electrodes were calculated using the Berzins-Delahay equation, which were 3.85 × 10^–5 and 7.42 × 10^–5 cm² s^–1, respectively. Similarly, the diffusion coefficients were also calculated using the Sand equation, which were 2.89 × 10^–5 and 4.55 × 10^–5 cm² s^–1, respectively. In addition, the deposition and dissolution behavior of Pb(II) on molybdenum and graphite electrodes were further investigated with chronopotentiometry (CP) and open circuit chronopotentiometry (OCP), respectively, and the results obtained were in agreement with the CV and SWV results. This study lays a foundation for the recycling of secondary Pb resources and the preparation of Ti–Pb alloys by electrodeposition method in molten salt.