Electrochemistry of Ta(V) in Lewis Basic TaCl5-EMIC Low Temperature Molten Salts

Abstract

The electrochemical reduction of Ta(V) in a TaCl5-EMIC (1-ethyl-3-methylimidazolium chloride) low temperature molten salt was investigated by using various voltammetric techniques. The melt composition was 66.7 mol% of EMIC, and all experiments were carried out at 373 K. Cyclic voltammograms showed two reduction waves on the forward scan followed by two oxidation waves on the reverse scan at potentials nobler than that of EMI+ reduction. The stoichiometry and the number of electrons in the reaction for each cathodic wave were examined by wave shape analyses of normal pulse voltammograms and differential pulse voltammograms. The results indicated that the first cathodic wave corresponded to the reduction of Ta(V) to Ta(IV), then Ta(IV) was reduced to Ta(II) in the second one. The effects of LiF addition into the melt on the reduction mechanism of Ta(V) were also studied, and a possibility of a further reduction of Ta(II) to metallic tantalum in the LiF-added melt was obtained.