关键词: 电沉积, 低共熔溶剂, 氯化胆碱-乙二醇, 锑, 循环伏安

Abstract:

Antimony is a chemically stable metal that has been widely used in industry, military and other fields. The use of electrodeposition to prepare antimony coating has the advantages of simple operation and low cost. The deep eutectic solvent (DES) is a eutectic mixture composed of a hydrogen bond donor and a hydrogen bond acceptor at a fixed molar ratio. It has the advantages of wide electrochemical window, high thermal stability, easy preparation, and low cost. Selecting DES as the electrolyte for electrodeposition can avoid the hydrogen evolution reaction of the aqueous system and the toxicity of ionic liquids. In recent years, there have been more and more researches on the preparation of metal coatings by electrodeposition in DES. In this work, choline chloride (ChCl) and ethylene glycol (EG) were heated and mixed at a molar ratio of 2:1 to form DES, while antimony(III) chloride (SbCl₃) was added to form an electrolyte. At room temperature, Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy were used to analyze the structure of the electrolyte. The results show that there were a large number of hydrogen bonds in DES, and that the existence of hydrogen bonds played an important role in the formation of DES. Sb(III) existed in the eutectic solvent in the form of [SbCl₄]^-. Using a three-electrode system, cyclic voltammetry was used to study the electrochemical behaviors in DES at different sweep speeds (25 ~ 55 mV·s^-1), different temperatures (333 ~ 363 K), and different concentrations (0.01 ~ 0.10 mol·L^-1) of Sb(III). The results indicate that at 343 K, the reduction of Sb(III) in ChCl-EG became a quasi-reversible reaction controlled by diffusion through one-step three-electron transfer. The diffusion coefficient at 343 K was 3.06×10^-9 cm²·s^-1. As the temperature and concentration of the electrolyte increased, the overpotential required for the reduction of Sb(III) decreased. The nucleation mode of electrochemical reduction of Sb(III) in ChCl-EG was studied by chronoamperometry. According to the Scharifker-Hills nucleation model, at 343 K, the nucleation of Sb on the tungsten electrode follows three-dimensional instantaneous nucleation. In addition, the electrodeposition products were characterized by SEM and XRD. SEM observations reveal that the applied deposition potential is the main driving force for the reduction of Sb(III). As the deposition potential increased from -0.33 V to -0.41 V, the morphology of the electrodeposition product gradually changed from granular crystals to dendrites. XRD data shows that there was Sb phase in the deposited product obtained at -0.41 V. In addition, the Cu₂Sb phase was presented due to the interfacial reaction between the newly deposited Sb and the substrate Cu to form intermetallic compounds. Future research can continually study the influences of such inorganic additives as boric acid (BA), ammonium chloride (NH₄Cl), and organic additives includingethylene-diaminetetraacetic acid (EDTA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) and Idranal VII (HEDTANa₃) on Sb electrodeposition.

Key words: electrodeposition, deep eutectic solvent, choline chloride-ethylene glycol, antimony, cyclic voltammetry