Electrochemical conversion of ionic liquid-lead sulfate paste into metallic lead or lead(IV) oxide: Extracting lead from water-insoluble lead salt and formation of cobalt oxide electrocatalyst via galvanic displacement.

Abstract Water-insoluble PbSO 4 only slightly dissolved in an amide-type hydrophobic protic ionic liquid (IL); the protonated betaine bis((trifluoromethyl)sulfonyl)amide ([Hbet][TFSA]). However, the paste of [Hbet][TFSA]-PbSO 4 coated on screen-printed carbon electrode (SPCE) could be electrochemically converted to Pb or PbO 2 in aqueous 0.1 M KCl via constant-potential electrolysis for the former and continuous cyclic voltammetry in 0.1 M NaOH for the latter. The formation of PbO 2 , which could be converted to CoO x (containing Co 3 O 4) through galvanic displacement in a Co(NO 3) 2 aqueous solution, was verified with Raman scattering spectroscopy and X-ray photoelectron spectroscopy (XPS); the latter also verified the formation of Co 3 O 4. The CoO x -modified electrode showed activity and high stability towards the oxygen evolution reaction (OER) in alkaline solutions. The approach shown in this study can be further developed as a procedure for extracting Pb metal or preparing CoO x catalysts from wastes, such as the discarded lead-storage batteries. Graphical abstract Unlabelled Image Highlights • A protic hydrophobic amide-type ionic liquid (IL) was mixed with PbSO 4 to be a paste. • The paste can be electrochemically converted to Pb or PbO 2. • PbO 2 can be further converted to Co 3 O 4 via galvanic displacement. • The Co 3 O 4 -modified PbO 2 electrode showed activity to oxygen evolution reaction. [ABSTRACT FROM AUTHOR]