Non-aqueous electrodeposition of Fe-Mn alloys using choline chloride based deep eutectic solvents

Deep eutectic solvents (DESs) are green anhydrous solvents that have recently been proposed in sustainable non-aqueous metal electrodeposition processes. The use of DESs over aqueous solutions allows metal electrodeposition without significant side reactions, such as the evolution of hydrogen gas, which is responsible for embrittlement phenomena. In the current work, the electrolytic deposition of Fe-Mn alloys, which present good application in temporary biomedical devices, using DESs was assessed. Three DESs were studied: (a) choline chloride and ethylene glycol (ChCl/EG), (b) choline chloride and glycerol (ChCl/Gly), and (c) choline chloride and urea (ChCl/Urea). The physicochemical properties (viscosity and conductivity) of the three DESs of interest, with and without the presence of dissolved Fe and Mn salts, were thoroughly studied. Cyclic voltammetry analyses showed that the reduction potential of both metals was within the potential window for the three DESs studied, which allowed the successful electrodeposition of Fe-Mn alloys. The deposit obtained from the ChCl/Urea DES presented the highest amount of Mn (49.71 at%). The latter, as well as the fact that the ChCl/Urea based electrolyte showed good stability at T = 80 °C after four electrodeposition cycles, are promising indicators of the potential success of the use of non-aqueous electrodeposition of Fe-Mn alloys using DESs.