Abstract
Among the Deep Eutectic Solvents (DESs), ethylene glycol-based one is attracting the attention of many researchers because of its relatively low viscosity with respect to analogous eutectic systems with urea, malonic acid or glycerol. In this work, the electrochemical behavior of Co(II) in a eutectic solution of choline chloride and ethylene glycol (1ChCl:2EG molar ratio) was investigated by cyclic voltammetry (CV) at 70°C followed by galvanostatic deposition (GD). The deposits on copper substrate were characterized with a field emission scanning electron microscope (FE-SEM) showing a nanostructured surface texture with platelet-like architecture resulting in a high hydrophobicity (contact angle CA >135°). By increasing the current density, more compact films were obtained while the addition of boric acid resulted in a finer structure. X-ray diffraction (XRD) analysis determined the coexistence of FCC and HCP phases, both with and without the addition of boric acid to the bath. Annealing in a nitrogen atmosphere was performed at different temperatures (300°C–600°C) to observe microstructure evolution. Magnetic properties with a coercivity of 60–80 Oe were measured by means of micro-indentation and Vibrating Sample Magnetometer (VSM).
Highlights
Choline chloride [HOC2H4(Cl)N(CH3)3] (Sigma Aldrich >99.8%),was dried under vacuum at 120◦C for more than 12 hours and subsequently mixed with ethylene glycol [C2H6O2] (Sigma Aldrich 99.8%), in the molar ratio 1ChCl:2EG
Potential scan toward negative values caused hydrogen evolution to occur at the Pt surface below −1.4 V vs Pt, where a steep decrease in the current was observed in the voltammogram
Electrochemical behavior of Co(II) solution of 1ChCl:2EG was assessed by means of cyclic voltammetry on a platinum substrate showing cathodic and anodic peaks corresponding respectively to Co reduction and stripping of the corresponding film
Summary
Choline chloride [HOC2H4(Cl)N(CH3)3] (Sigma Aldrich >99.8%),was dried under vacuum at 120◦C for more than 12 hours and subsequently mixed with ethylene glycol [C2H6O2] (Sigma Aldrich 99.8%), in the molar ratio 1ChCl:2EG. The existence of a cobalt deposit was confirmed by EDS analysis on the working electrode surface after potentiostatic deposition runs in the potential range of −0.9 to −1.15 V vs Pt. During the reversal sweep, the corresponding anodic peak was observed around −0.15 V vs Pt, where the cobalt film formed during the forward scan was stripped
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