Dissolution-electrodeposition pathway and bulk porosity on the impact of in situ reduction of solid PbO in deep eutectic solvent

Abstract

The verification of dissolution-electrodeposition pathway and bulk porosity on the impact of in situ electrochemical reduction of solid PbO in choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES) is systematically clarified at cell voltage 2.5V and 353K. Cyclic voltammetry of the microelectrode loaded with PbO powders in PbO-ChCl-EG saturated solution exhibits that an additional reduction peak corresponding to the deposition of [PbO·Cl·EG]− is observed. There is no conspicuous difference in morphologies between the products obtained from saturated PbO-ChCl-EG and ChCl-EG DES. The effects of bulk porosity of PbO pellet on the deoxidation process, phase composition and morphologies of products are investigated. When the adding amount of NH4HCO3 and bulk porosity of PbO pellet are about 50% (in weight) and 54.49% (in volume) respectively, the reaction rate of PbO to lead is the fast in the range of present study. Moreover, the direct electro-reduction models of PbO pellet in dense and porous form in ChCl-EG DES are proposed and it emphasizes that the bulk porosity plays an important role because a larger porosity allows a faster diffusion of ions and a higher solubility of PbO into [PbO·C·EG]− which is strongly in favor of the deposition pathway. This method not only forms the scientific base for a scientifically electrolytic extraction of metallic lead but also opens an avenue to the electrochemical fabrication of other metals and alloys from oxide precursors.