Kinetic investigation of zinc electrodeposition from sulfate electrolytes in the presence of impurities and ionic liquid additive [BMIM]HSO4

The effects of some common impurities such as copper, iron, nickel, cobalt, lead and their interaction with an ionic liquid additive 1-butyl-3-methylimidazolium hydrogen sulfate-[BMIM]HSO4 on zinc electrodeposition from acidic sulfate electrolyte were characterized in terms of the polarization behavior and the kinetics of zinc deposition using cyclic voltammetry and potentiodynamic polarization measurements. The results showed that these metallic impurities studied exerted some different changes in cyclic and cathodic polarization voltammograms. The addition of [BMIM]HSO4 was observed to counteract the detrimental effects of these impurities and induced a blocking effect on the zinc electrodeposition process through its cathodic adsorption on the electrode surface. The adsorption of this additive shifted the electroreduction potential of zinc ions towards more negative values, restricted impurities ions from being electroreduced, and inhibited hydrogen evolution. Moreover, the kinetics analysis of cathodic polarization suggested that the presence of these impurities alone and in combination with [BMIM]HSO4 had no effect on the Tafel slope and transfer coefficient but affected the exchange current density for the zinc deposition. (C) 2012 Elsevier B.V. All rights reserved.