A comparative evaluation on the anodic behavior of Cu and Ag electrodes in non-aqueous fluoride and fluoroborate media |
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Authors: | V Suryanarayanan M Noel |
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Institution: | (1) Electro Organic Division, Central Electrochemical Research Institute, Karaikudi, 630 006, India |
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Abstract: | The voltammetric responses of copper and silver had been extensively studied and compared in a variety of non-aqueous solvents
such as acetonitrile (AN), propylene carbonate (PC) and sulfolane containing two different supporting electrolytes namely
triethylaminetrishydrogen fluoride (TEA.3HF) and tetrabutylammonium tetrafluoroborate (TBABF4). The dissolution rate and surface transformation on the electrode surfaces as a result of anodic polarization was investigated
using atomic absorption spectroscopy (AAS) and scanning electron microscopy (SEM), respectively. In solvent-free TEA.3HF medium,
the copper electrode shows high charge recovery ratio (Q
c/Q
a), and the difference between the initial anodic and cathodic potentials, obtained at a current density of 2 mA cm−2, is around 0.11 V, suggesting that in this medium, Cu can certainly serve as reference electrode. On the other hand, on Ag
electrode, substantial dissolution was observed leading to very high anodic (Q
a) and cathodic (Q
c) charges, and the surface morphology after the cyclic polarization results in roughened surface with large pores. The effects
of incorporating AN and water as additives in TEA.3HF on the solubility and stability of these metal fluoride films are also
reported. The dissolution pattern and film formation behavior of these two metals in the different solvents containing fluoride
and fluoroborate ionic species have several qualitative similarities, as noted from cyclic voltammetry responses and SEM morphology.
Anodic dissolution and precipitation process for both Cu and Ag depends significantly on the nature of supporting electrolytes
as well as solvents. In AN containing 0.1 M TEA.3HF, the dissolution of Cu and Ag electrodes was very high. Fluoride salts
of Cu show lesser solubility than Ag in those solvents, while fluoroborate salts exhibit the reverse trend. The AAS data suggest
that for a particular salt, which may be either fluoride or fluoroborate of Cu and Ag, the relative solubility decreases in
the order AN > PC > sulfolane. |
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Keywords: | |
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