Electrochemical study of copper in a basic 1-ethyl-3-methylimidazolium tetrafluoroborate room temperature molten salt

The electrochemistry and electrodeposition of copper was investigated on polycrystalline tungsten, platinum and on glassy carbon electrodes in 1-ethyl-3-methylimidazolium tetrafluoroborate room temperature molten salt containing excess 1-ethyl-3-methylimidazolium chloride. Experiments performed in a N₂-filled dry box show that Cu(I) can be oxidized to Cu(II) or reduced to Cu metal. The Cu(I)/Cu(II) redox couple exhibits a quasi-reversible charge-transfer behavior. The electrodeposition of copper on the platinum electrode was proceeded by underpotential deposition (UPD), whereas the electrodeposition of copper at glassy carbon and tungsten electrodes requires a nucleation overpotential. Although under ambient atmosphere, this melt absorbs some moisture, it is still stable because no significant difference was observed between the staircase cyclic voltammograms of the melt itself obtained in a N₂-filled glove box and under ambient air. The electrochemical behavior of copper in this melt under the ambient atmosphere is very similar to that observed under the glove box atmosphere, except that Cu(I) spontaneously converts to Cu(II) in ambient air. Electrodeposits of Cu were obtained from experiments performed both in a glove box and under ambient atmosphere. Scanning electron microscope (SEM) results showed that the deposits were fairly dense.