Effects of ionic liquid additive [BMIM]HSO4 on copper electro-deposition from acidic sulfate electrolyte

The effect of a new ionic liquid additive 1-butyl-3-methylimidazolium hydrogen sulfate-[BMIM]HSO4 on the kinetics of copper electro-deposition from acidic sulfate solution was investigated by cyclic voltammetry, polarization and electrochemical impedance measurements and compared with those exerted by the conventional additive, thiourea. Results from cyclic voltammetry and kinetic parameters such as Tafel slope, transfer coefficient and exchange current density obtained from Tafel plots, indicated that [BMIM]HSO4 had a pronounced inhibiting effect on Cu2+ electro-reduction and led to more leveled and fine-grained cathodic deposits. In addition, [BMIM]HSO4 was found to inhibit the charge transfer and slightly change the copper electro-deposition mechanism compared to the absence of additives. Data obtained from X-ray diffraction spectra revealed that the presence of these additives did not change the crystal structure of the electro-deposited copper but strongly affected the crystallographic orientation of the crystal planes.