Study On Electrodeposition Of Nickel And Silver In ChCl-EG Eutectic Solvent

The eutectic solvent is a kind of ionic liquid,which is an emerging green solvent in the past 30 years and is widely used in the field of electrodeposition.Choline Chloride-Ethylene Glycol(ChCl-EG)eutectic solvent has higher resource interest rate and less pollution than traditional water solvent,and the preparation conditions are simple and can be reused.Since the eutectic solvent belongs to a non-aqueous system,the disadvantages of water in electrodeposition are avoided.In this paper,the structure and physicochemical properties of ChCl-EG eutectic solvent were studied first.The test methods include infrared spectroscopy and conductivity test.Cyclic voltammetry,linear cyclic voltammetry,and chronoamperometry were used to study the electrochemical behavior and nucleation of metals in eutectic solvents.A coating obtained by electrodeposition in this system.Scanning electron microscopy(SEM)was used to observe and analyze the microstructure,and EDX was used to analyze the elements of the coating to observe the elemental composition of the coating.After determining the element composition,the existing form of the metal element in the plating layer is further analyzed,and the XRD characterization method is used.XPS testing techniques were used in studying the valence state of rare earth element lanthanum in the coating.UV-visible testing techniques were also used in studying the effects of additives.The results of nickel in the ChCl-EG eutectic solvent system show that nickel is controlled by the diffusion step,and electrodeposition is a quasi-reversible reaction,and nickel belongs to three-dimensional transient nucleation in the nucleation process.The nickel electrodeposited layer is evenly distributed on the copper substrate,and the plating layer contains only nickel.And the nickel plating layer with high purity and uniform distribution can be obtained by the ChCl-EG eutectic solvent system.Studies on the addition of rare earth lanthanum show that the addition of cerium(?)does not change the nucleation mode of nickel ions.With or without cerium ions,the nucleation process of nickel is three-dimensional transient nucleation.And the addition of cerium(?)ions can reduce the activation energy when nickel ions are reduced.The addition of niobium makes the nickel coating more excellent in microscopic morphology and improved in corrosion resistance in hydrochloric acid solution.The results of the electrodeposition of silver using a non-aqueous solvent ChCI-EG eutectic solvent showed that a silver plating layer was obtained on the copper substrate.The electrochemical behavior of silver ions in ChCI-EG eutectic solvent was investigated.Silver is an irreversible process controlled by the diffusion step in the ChCl-EG eutectic solvent,and the diffusion coefficient is 1.14873 x 10"7 cm2·s-1.With the increase of potential,the nucleation process of silver ions has a tendency to develop from three-dimensional instantaneous nucleation to three-dimensional continuous nucleation.The silver deposit is evenly distributed on the surface of the substrate.The silver plating obtained by electrodeposition was cubic,and the average size was 23 nm.The results of EDTA on the effect of electrodeposited silver in ChCI-EG eutectic solvent system show that the addition of EDTA will change the color of the original solvent,and the color change is determined by UV test,which is new due to EDTA and Ag+.Complex.The addition of EDTA causes the nucleation process of silver ions to change from three-dimensional transient nucleation to three-dimensional continuous nucleation.Moreover,by adding EDTA,the degree of cathodic polarization of the solution is increased,and the crystal grains can be refined.In this paper,preliminary studies on electrodeposited silver-tin plating have been carried out.The experimental results show that Sn2+ basically meets the reversible process conditions when it is reduced alone,showing a reversible process,and the irreversible process is shown in the mixed solution.Different ratios of Ag and Sn have an effect on the composition of the coating.When Ag:Sn=2:1,the coating mainly exists in the form of Ag3Sn:when Ag:Sn?l:l,the coating mainly exists in the form of Sn,Ag3Sn and Ag4Sn;when Ag:Sn=1:2,The coating is mainly present in the form of elemental Sn.