Electrochemical synthesis of cobalt with different crystal structures from a deep eutectic solvent

The present paper shows experimental evidence of electrochemically synthetizing cobalt with hexagonal and face centered cubic structures from a choline chloride-based deep eutectic solvent. The nucleation and diffusion-controlled growth mechanisms of cobalt onto a copper electrode were studied through electrochemical means in order to determine several kinetic parameters of interest such as the nucleation rate, A, and the number density of active sites, N0. Current density transients were analyzed using a model comprising the simultaneous presence of cobalt 3D nucleation with diffusion-controlled growth and residual water reduction on the growing surfaces of the metallic nuclei. The massive electrodeposition of cobalt was carried out on copper substrates using potentiostatic and galvanostatic techniques. The analysis of results obtained from the surface deposit microstructure and morphology using scanning electron microscopy images and magnetic measurements, confirmed the existence of the hexagonal and cubic cobalt structures. It was found that fiber textures parallel to the electrodeposition axis are formed in the case of the cobalt cubic structure. Furthermore, mainly the current density and kinetics of crystallites nucleation are considered the key parameters to favor the crystal structure change, thus formation of the texture of cobalt from DES.