Cation catalysis in high-temperature electrochemical synthesis of tungsten carbides in molten salts

Author(s): Sergei V.Volkov, Inessa A.Novoselova, Veniamin V.Solovyev, Lyudmila A.Chernenko*

The paper presents a quantum-chemicalmodel and experimental confirmation of cation catalysis phenomenon by the influence of magnesium cation on tungstate anion electroreduction to metallic tungsten in a chloride melt. Ab-initio calculations of the parameters of the {Mgn 2+[WO4]2-}(2n-2)+ type species have been performed.Within the framework of this approximation the compositions for the most stable species in molten salts were obtained. The peculiarities of electroreduction of tungstate anion and carbon dioxide have been studied by the method of cyclic voltammetry in the binaryNaCl- KCl melt on platinum electrodes at 7500C separately and jointly, in the presence and without magnesium chloride. It has been shown that addition of Mg2+ in the melt is a necessary condition for the electrodeposition of tungsten in the same potential range as carbon from carbon dioxide and for the subsequent synthesis of tungsten carbides. The electrochemical synthesis of tungsten carbides WC and W2C in the form of dispersed powder has been effected in the system NaCl-KCl-Na2WO4-MgCl2-CO2. The optimal electrolysis conditions have been determined for the synthesis of single-phaseWC powder. WC product was produced in the studied systemwith electrodeposition rate 0.3 g/A·h at CO2 pressure over 1.7MPa and at cathodic current densities 0.05 – 0.2 A/cm2.

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