Cationic electrocatalysis in effecting the electrosynthesis of tungsten carbide nanopowders in molten salts

Abstract

The chapter presents the theoretical and experimental concepts of the phenomenon of cationic electrocatalysis during the discharge of complicated anionic complexes in molten salts. These ideas are based on the acid-base mechanism of formation of electrochemically active species (EASs). The essence of cationic electrocatalysis is the transformation of anionic complexes into a new active state under the action of cations with a strong polarizing effect. This leads to a change in the energy, electronic, and structural state of the anion, the formation of new EASs, a change in their composition, in the rate of EAS formation and charge transfer. The performed quantum chemical calculations allow one to conclude that the cationic composition of the melt catalyzes the formation of new EASs both in the bulk phase of the melt and at the electrode-melt interface. Using voltammetry, it was shown that the addition of Mg2+ cations to tungstate-containing melts leads to a change of the nature of the electrode process and to an increase of an order of magnitude in heterogeneous rate constant for charge transfer. The tungsten deposition potential shifts to the positive potential values up to the potentials of carbon deposition from CO2. The proposed approach allowed us to realize in practice the synthesis of nanoscale powders of tungsten carbides and composite mixtures based on them by electrolysis of molten salt electrolytes. The obtained materials have a high potential for application for solving various tasks of electrocatalysis.