Electrochimica Acta 55 (2010) 5407–5410 Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta Electro-generated nickel/carbon nanotube composites in ionic liquid P. Martis, V.S. Dilimon, J. Delhalle, Z. Mekhalif ∗ Laboratory of Chemistry and Electrochemistry of Surfaces (CES), University of Namur (FUNDP), 61 Rue de Bruxelles, B-5000 Namur, Belgium article info Article history: Received 7 January 2010 Received in revised form 12 April 2010 Accepted 18 April 2010 Available online 27 April 2010 Keywords: Electrodeposition Composite MWCNTs Deep eutectic solvent Ionic liquid abstract It is reported, for the first time, that compact nickel-multiwalled carbon nanotube (Ni/MWCNT) compos- ites were successfully electrodeposited in choline chloride/urea based deep eutectic solvent (DES) on a copper substrate. Dispersion stability of MWCNTs is excellent in DES nickel chloride solution therefore electrodeposition of Ni/MWCNT composites was easily achieved. MWCNTs were uniformly distributed in the nickel matrix and gave different morphologies and high surface roughness to the coating. Coating with oxygen-functionalized MWCNTs exhibited higher stability and better corrosion resistance than the coating with pristine MWCNTs. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction Electrodeposition of metal carbon nanotube composites attracts a lot of interest owing to their extraordinary specific stiffness and strength [1]. Nickel/multiwalled carbon nanotube (Ni/MWCNT/) composites possess promising potential features, such as enhanced hardness, excellent solid lubrication, protection against corrosion and catalytic performance [2]. However, MWCNTs are largely inert and do not disperse well in aqueous solutions, so uniform deposi- tion of MWCNTs in the metal composites is a difficult task without the addition of surfactants or dispersants [3]. Therefore, it is impor- tant to explore possibilities of finding a compatible solvent which could, at the same time, show good dispersion stability for MWC- NTs and conductive. In this regard, ionic liquids are fast emerging as promising alternative solvents for electrochemistry purposes [4–7]. DES is a new class of ionic liquid typically formed by mixing choline chloride (as quaternary ammonium salt) with hydrogen bond donors such as amides, acids and alcohols [8,9]. Abbott et al. have shown that DES can be successfully employed in electropol- ishing, electroplating and electroless deposition [10–12]. Recently they have also shown that choline chloride and either urea or ethy- lene glycol based DES can be employed in the electrodeposition of zinc–tin alloys, copper composites and nickel [11,13,14]. In the current study, for the first time, we make an attempt to study the feasibility of DES to electrodeposit Ni/MWCNT com- posites. Firstly, dispersion stability of both pristine MWCNTs ∗ Corresponding author. Tel.: +32 81 72 52 30. E-mail address: zineb.mekhalif@fundp.ac.be (Z. Mekhalif). (P-MWCNTs) and oxidized MWCNTs (O-MWCNTs) was studied in DES in comparison to aqueous media. Then electrodeposited Ni/MWCNT composites were investigated in relation to their sta- bility, morphology and electrochemistry. 2. Experimental 2.1. Preparation of Ni/MWCNT coatings P-MWCNTs (NC-3100) (purity > 95%) having an average diam- eter of 10 nm and length of several micro-meters (0.1–10) were procured from Nanocyl S.A. The P-MWCNTs were treated with a conc. H 2 SO 4 :conc. HNO 3 (3:1) solution at 50 ◦ C for 8 h to gener- ate oxygen functionalities on the surface to get O-MWCNTs. The detailed procedure is given in our previous paper [15]. The copper plate having 1 cm 2 working surface area was pol- ished (Buehler-Phoenix 4000) successively with 1200 grit silicon carbide paper and diamond paste suspensions (particle size 9, 3 and 1 m, respectively) to get a mirror finish. The copper plate was washed with ultra-pure (18 M cm) water and sonicated in ace- tone for 15 min and dried immediately with high-purity nitrogen stream. The plating bath was prepared from reagent grade chemi- cals (purity > 98%) and was used as such. The choline chloride/urea based DES was prepared following the previous report [8]. Nickel solution (0.3 M) in DES was prepared from anhydrous NiCl 2 . The amount of MWCNTs in the nickel solution was 0.1 g/L. The suspen- sion of MWCNTs in the NiCl 2 solution was ultrasonicated for 10 min to get a stable dispersion. Before electrodeposition, the copper electrode surface was acti- vated by immersing into a 10% sulfuric acid solution for 30 s. All 0013-4686/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2010.04.065