Conversion of Nb2O5 to NbS2 for the Preparation of Niobium Nanopowder through Solid Cathode Electrolysis in Molten Chlorides

Niobium (Nb) is primarily used as the active material in Nb electrolytic capacitors in the form of metallic fine powder. Unlike traditional methods of preparing niobium powder through chemical or electrochemical reduction of metal compounds in molten salts, we report here the efficient preparation of Nb nanopowder via electrolysis of NbS 2 in the NaCl-KCl melt at 973   K. The NbS 2 is simply synthesized by carbo-sulfidation of Nb 2 O 5 . The following electro-desulfidation in the molten electrolyte converts solid NbS 2 into Nb nanopowder at the cathode, with S 2- ions moving to the anode and being oxidized to gaseous sulfur. The reduction path was verified to be NbS 2 → L x NbS 2 → NbS 2-w → Nb. Through constant cell electrolysis at 2.9   V, NbS 2 is rapidly reduced to nodular Nb nanopowder (50-100   nm), with a Current efficiency and energy consumption of approximately 94% and 3.58   kW·h kg⁻¹ Nb, respectively.