Journal of the Electrochemical Society, Vol.142, No.6, 1758-1765, 1995
Electrochemical and Spectroscopic Studies of Tungsten-Species in the AlCl3-Naclsat Melt
The electrochemical behavior of KWCl6 in the AlCl3-NaClsat melt at 175 to 200 degrees C was investigated using multiple electrochemical methods : cyclic, normal pulse, square wave voltammetries, chronoamperometry, and exhaustive electrolysis. Electronic spectroscopy and x-ray diffraction methods were employed to characterize the products formed at different potentials. The melt was treated with CCl4 to remove oxide impurities. It was found that the reduction sequence of W(V) was dependent on the scan rate, i.e., at fast scan rates three main redox couples were observed, while additional redox couples appeared in low scan rate voltammograms. To reach a better understanding of the mechanism, some low oxidation state tungsten compounds (K2WCl6 and W6Cl12) were also examined. The reduction of W(V) to tungsten metal involves several intermediate oxidation states and cluster species, such as W(IV), unstable W(III), dimers W(IV, III) and W(III,II), [W6Cl8](4+) and its one-electron reduction product. Partial characterization of some of the intermediate reduction products has been achieved.
Keywords:SQUARE-WAVE VOLTAMMETRY;SODIUM CHLOROALUMINATE MELT;DROPPING MERCURY-ELECTRODE;HALIDE CLUSTERS;MOLYBDENUM(II);COMPLEXES;CHLORIDE;BEHAVIOR;OXIDE;IONS