On the Control and Effect of Water Content during the Electrodeposition of Ni Nanostructures from Deep Eutectic Solvents

Abstract

The electrodeposition of nickel nanostructures on glassy carbon was investigated in 1:2 choline chloride urea (1:2 ChCl-U) deep eutectic solvent (DES) containing different amounts of water. By combining electrochemical techniques, with ex-situ FE-SEM, HAADF-STEM and EDX, the effect of water content on the electrochemical processes occurring during nickel deposition was better understood. At highly negative potentials and depending on water content, Ni growth is halted due to water splitting and the formation of a mixed layer of Ni/NiO x (OH) 2(1−x)(ads). Moreover, under certain conditions, the DES components can also be (electro)chemically reduced at the electrode surface, blocking further 3D growth of the Ni NPs. Hence, a 2D crystalline Ni containing network can be formed in the inter-particle region. in the inter-particle region. Careful tuning of the water content leads to a fine control of the deposition potentials of Ni and the side reactions occurring at more negative potentials, giving the ability to control self-limiting growth and passivation phenomena. Supporting Information Available Water content. The 3 rd scan of the CVs of Figures 1, 2 and 3. Influence of stirring. Selected area electron diffraction (SAED).

Water distribution at the electrified interface of deep eutectic solvents

“…Here it is also important to mention that prior studies of electrodeposition of nickel from Reline DES with different amounts of water (#10 wt%) showed the adsorption and electrolysis of water are remarkable at high cathodic potentials (E # À0.9 V vs. Ag QRE). 56 Alternatively, at the positively charged electrode, the interfacial region starts accommodating water even at a lower surface charge and further increasing the electrode charge leads to the accumulations of a higher amount of water molecules in the interfacial region. This is shown in Fig.…”

“…Recently, this has been conrmed experimentally using combined electrochemical and surface analysis techniques. 56,57 On the other hand, in closed electrochemical systems, such as batteries and supercapacitors, high surface polarization leads to electrolysis of water in the vicinity of the electrode surface which results in formation of hydrogen and oxygen gas. Because of the gas formation, the internal pressure increases and the active site/pores of the electrode surface are blocked by the gas bubbles.…”

Influence of water content and applied potential on the electrodeposition of Ni coatings from deep eutectic solvents

“…Its content was quantified by Karl Fischer titration while performing the electrochemical measurements. In order to limit the concentration of water, a set of electrochemical measurements were also performed in an argon controlled atmosphere glovebox (JACOMEX GP[CONCEPT]) [27].…”

“…(5). These phenomena, water and choline reduction at lower overpotentials, result in the macroscopic changes in the Ni coating appearance [27].…”

Ni/cerium Molybdenum Oxide Hydrate Microflakes Composite Coatings Electrodeposited from Choline Chloride: Ethylene Glycol Deep Eutectic Solvent

“…By changing the water content, one can control the potential for Ni deposition. Potential Ni impacts the self-limiting growth crystallite and passivation effect [11]. In addition to the above advantages, DESs liquids enable the electrodeposition of nickel alloy coatings: Zn-Ni [12], Ni-Co-Sn [13], Fe-Ni [14], Ni-Co [15], Ni-Mo [16], and nickel composite coatings.…”