Influence of alkylpyridinium ionic liquids on copper electrodeposition from acidic sulfate electrolyte

The effect of two alkylpyridinium ionic liquids (py-iLs) including N-butylpyridinium hydrogen sulfate (BpyHSO4 ) and N-hexylpyridinium hydrogen sulfate (HpyHSO4 ) on the kinetics of copper electrodeposition from acidic sulfate solution was investigated by cyclic voltammetry and potentiodynamic polarization measurements. Results from cyclic voltammetry indicate that these py-iLs have a pronounced inhibiting effect on Cu2+ electroreduction and there exists a typical nucleation and growth process. Kinetic parameters such as Tafel slope, transfer coefficient and exchange current density obtained from Tafel plots, lead to the conclusion that py-iLs inhibit the charge transfer by slightly changing the copper electrodeposition mechanism through their adsorption on the cathodic surface. In addition, scanning electron microscope (SEM) and X-ray diffraction analyses reveal that the presence of these additives leads to more leveled and fine-grained cathodic deposits without changing the crystal structure of the electrodeposited copper but strongly affects the crystallographic orientation by significantly inhibiting the growth of (111), (200) and (311) planes.