Abstract: The electrodeposition of metallic Co from a 1-ethyl-3-methylimidazolium chloride (EMIC) ionic liquid containing ethylene glycol (EG) and CoCl2 was investigated on copper substrates. Cyclic voltammogram indicated that the redox waves increased with increasing ethylene glycol content, because ethylene glycol accelerated the ionization of EMIC. The electrodeposition of metallic Co in EMIC-CoCl2-EG electrolyte was controlled by diffusion and irreversible growth process. At Pt electrode the cathodal transfer coefficient (α) and diffusion coefficient (D0) of Co(II) in EMIC-CoCl2-EG electrolyte were determined. Their values were obtained as follows: α=0.30 and D0=4.16×10^-6 cm·s^-1. Chronoamperometric results indicated that the electrodeposition of metallic Co at Pt electrode belonged to a three-dimensional progressive nucleation mechanism. The micromorphology of electrodeposits was observed by field emission scanning electron microscopy (FE-SEM). SEM images of the electrodeposits showed that the crystallite was small and compact. X-ray diffraction (XRD) approved that the obtained electrodeposits were pure cobalt. The results indicated that metallic Co electrodeposited from the 1-ethyl-3-methylimidazolium chloride ionic liquid containing ethylene glycol and CoCl2 was a mixed phase of crystalline and microcrystalline. The average size of cobalt crystalline grain was several tens nanometers.

Key words: Cobalt, 1-ethyl-3-methylimidazoliumchloride, Ionic liquid, Electrodeposition, Electrocrystallization