Electrodeposition of Nickel from Deep Eutectic Solvents

Electrodeposition is an important technology for several applications such as the fabrication of metallic coatings, elaboration of semiconductor thin films for photovoltaics and synthesis of nanomaterials. Compared to physical vapor deposition techniques (e.g. sputtering), electrodeposition is especially interesting for large area surface treatments at the industrial scale, due to its versatility and low cost. Furthermore, electrodeposition permits the growth of the nanostructures directly on the substrate of interest and allows obtaining highly electroactive nanostructures [1]. Over the last few years Deep Eutectic Solvents (DESs) have generated great enthusiasm as a new generation of non-aqueous electrolytes. They offer plenty of advantages, such as high thermal stability and broad electrochemical window compared to aqueous solutions. Furthermore, DESs are less toxic and their preparation is less demanding and more cost-effective than this of Room Temperature Ionic Liquids (RTILs) [2].
In the present work, we investigated the electrodeposition of nickel on both glassy carbon (GC) and low carbon steel substrates from 1:2 choline chloride – urea DES (1:2 ChCl-U). The GC was used to generate supported nanostructures. Alternatively, the Ni films were sought after when using steel substrates. In both cases, by combining electrochemical techniques, such us cyclic / linear sweep voltammetry and chronoamperommetry, with ex-situ characterization, like FE-SEM, XPS, STEM, EDX and EELS, the electrochemical processes occurring during nickel deposition were better understood. Special attention was given to the interaction between the solvent and the electrodeposited nickel phase. This interaction has been shown to be very different from that in the aqueous solutions [3-4].

[1] G-R. Li, H. Xu, X-F. Lu, J-X. Feng, Y-X. Tong, C-Y. Su, Nanoscale, 5 (2013), 4056.
[2] E.L. Smith, A.P. Abbott, K.S. Ryder, Chem. Rev., 114, (2014), 11060.
[3] J.A. Hammons, T. Muselle, J. Ustarroz, M. Tzedaki, M. Raes, A. Hubin, et al., J. Phys. Chem. C., 117 (2013) 14381.
[4] E.A. Mernissi Cherigui, P. Bouckenooge, K. Sentosun, H. Vanrompay, S. Bals, H. Terryn, J. Ustarroz, Manuscript in Preparation, (2016).