Electrodeposition of Co, Sm and SmCo from a Deep Eutectic Solvent

The suitability of 1 choline chloride:2 urea mixture, Deep Eutectic Solvent (DES) for the electrodeposition of cobalt, samarium and cobalt–samarium system has been studied. Its electrochemical window permits deposition analysis to be carried out without interference from parallel reactions. Deposition was studied at 70 C in order to stimulate mass transfer and to lower solution viscosity. Cobalt deposits according to a nucleation and three dimensional growth mechanism, all its characteristic features do appear for all cases studied. Samarium deposition takes place through a more complex process in which a first potential range is found where the species formed limit the conductive character of the substrate. When potential becomes more negative, normal behaviour is observed. When both cobalt and samarium are present in the solution, codeposition occurs, at no potential value, any current diminution of the current was recorded under stirred conditions. Deposits of SmCo show different morphology and composition depending on applied potential. Nodular cobalt-rich deposits are obtained at low deposition potentials whereas fine grained samarium-rich ones are obtained at more negative deposition potentials.