Direct Electrochemical Desulfurization of Solid Sb2S3 to Antimony Powders in Deep Eutectic Solvent

Abstract

Antimony (Sb) powders and sulfur nanoparticles have been prepared by direct electroreduction of solid Sb2S3 in ChCl-EG DES at 353 K. Cyclic voltammogram of Sb2S3 on Pt-powder cavity microelectrode demonstrates that the electrochemical desulfurization of Sb2S3 to metallic Sb is a one-step process through three-electron transfer. Constant voltage electrolysis indicates that Sb2S3 can be completely transformed into metallic Sb and sulfur for 16 h, and the cathodic current efficiency is about 50.64%. Besides, ESI-MS analysis implies that four-coordinated complex anions [SbCl4]− are formed and the electrodeposition of [SbCl4]−→Sb0 also exists simultaneously except for the mainly direct desulfurization process. Dissolved Sb(III) ions can be reduced and deposited at Sb grains to form larger hemispherical particles in a more stable state, which looks like a snail shell to encapsulate these Sb grains. In addition, amorphous sulfur powders are densely agglomerated with each other to establish a network structure and the morphology is irregularly globular with diameters of 14–25 nm. The electro-desulfurization process of Sb2S3 powders has been analyzed and a schematic illustration is also proposed. This finding provides a possible way for green extraction of Sb from stibnite resources in DESs at near room temperature with short process and emission-free SO2.