Application of the Electrochemical Quartz Crystal Microbalance for the Investigation of Metal Depositions from Ionic Liquids

Abstract

Electrochemical quartz crystal microbalance was successfully applied to study the deposition of Ta from ionic liquids and for estimating the activation energy of viscosity of the 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [P 1,4 ] -TFSA ionic liquid. It could be shown that Ta electrodeposition occurs in several steps and that the deposited species were not always elemental Ta. Higher temperatures favoured the deposition process of pure Ta. Furthermore, the cation of the ionic liquid could influence the deposition process.

On the electrodeposition of tantalum from three different ionic liquids with the bis(trifluoromethyl sulfonyl) amide anion

“…1b shows that not all deposited material is dissolved during anodic stripping in [PMIm][TFSA], similar to the previous results obtained in [BMP][TFSA] or in [EMIm][TFSA]. 26 The apparent molar mass for the system TaF 5 /[PMIm][TFSA] was calculated for different potential regimes. When the deposition was carried out at 25 1C, an apparent molar mass of 47-75 g mol À1 was obtained between À1.4 and À2.5 V (Table 1).…”

“…Two peaks were obtained starting from the second cycle in 0.5 M TaF 5 in [PMIm][TFSA] at high temperatures (not shown). As no mass increase could be detected in the potential regime around the first cathodic peak (C 1 ) in 0.5 M TaF 5 in [EMIm][TFSA] or in [BMP][TFSA], 26 we tentatively assigned this first peak to the partial reduction of Ta(V). In passing we note that TaF 3 is a stable compound.…”

“…The CVs obtained for 0.5 M TaF 5 in [BMP][TFSA] and in [EMIm][TFSA] were already discussed in our previous paper. 26 The results obtained there will be shortly summarized below.…”

“…We showed in a previous paper that elemental tantalum is not always obtained during potentiodynamic experiments in the potential regimes where EQCM indicated a mass increase. 26 A major problem discussed in ref. 26 arises from the fact that the reactive transition elements can form non-stoichiometric tantalum halides.…”

“…26 A major problem discussed in ref. 26 arises from the fact that the reactive transition elements can form non-stoichiometric tantalum halides. The temperature proved to be a crucial parameter and elemental tantalum could only be obtained when the potentiodynamic experiments were performed in 0.5 M TaF 5 in [BMP][TFSA].…”