The effect of quaternary ammonium-based ionic liquids on copper electrodeposition from acidic sulfate electrolyte

The effect of quaternary ammonium-based ionic liquids (ILs) including tetraethylammonium hydrogen sulfate (NEt4HSO4) and tetrabutylammonium hydrogen sulfate (NBu4HSO4) on copper electrodeposition from acidic sulfate electrolyte was investigated by cyclic voltammetry and chronoamperometric measurements. These ILs were found to have a blocking effect on the copper electroreduction and induced the formation of more leveled and fine-grained cathodic deposits. Analysis of the dimensionless current-time transients indicated that the electrodeposition of copper was involved with instantaneous three-dimensional nucleation with diffusion-controlled growth. The addition of ILs induced the instantaneous nucleation to more progressive one. Data obtained from X-ray diffraction spectra revealed that the presence of these ILs strongly affected the crystallographic orientation of the electrodeposited copper with a (220) preferential orientation.