Influence of additive on electrodeposition of pure cobalt from an ionic liquid

In a l-ethyl-3-methylimidazolium chloride(EMIC) ionic liquid and ethylene glycol(EG) containing CoCl ₂, some analytic methods studied the influence of additive on electrodeposition of cobalt, such as field emission scanning electron microscope (FE-SEM), cathodic polarization curves, cyclic voltammograms, and X-ray diffraction. The results indicated that the electrodeposits appearance was improved remarkably with the addition of 2-Butyne- 1.4-diol into EMIC-CoC1 ₂-EG electrolyte, and smooth and silver gray electrodeposits with metallic luster can be obtained under the quantity range of 2-Butyne-1.4-diol was 0.3-0.7 g • L ^-1 FE-SEM images of electrodeposits showed that the crystals of metallic cobalt became finer after the addition of 2-Butyne-l.4-diol into EMIC-CoCl ₂-EG electrolyte. Cathodic polarization curves indicated that the addition of 2-Butyne-l.4-diol not only eliminated the underpotential deposition of cobalt but also increased the cathodic polarization. Cyclic voltammograms tests proved that the additive had inhibitive effects on the process of cathode deposition. X-ray diffraction(XRD) approved that the width of diffraction peaks for Co was increased and the size of crystallite grains was several nanometers, when 2- Butyne-1.4-diol was added into EMIC-CoCl ₂-EG electrolyte.