Effect of Additives on Electrodeposition of Copper in Ch Cl-Gl A Low Eutectic Solvent
The use of additives facilitates the deposition of copper on metal substrates.In this work,using choline chloride glacial acetic acid(Ch Cl-Gl A)as a low eutectic solvent and copper acetate as the main salt,the effects of ascorbic acid(C6H8O6),disodium ethylenediamine tet-raacetic acid(EDTA-2Na)and diethylenetriaminepentaacetic acid(DTPA)as additives on electrodeposition of copper on iron substrate were in-vestigated.Electrochemical behavior was studied by cyclic voltammetry(CV)and chronoamperometry(CA);scanning electron microscopy(SEM)and X-ray diffraction(XRD)were used to observe and analyze the morphology and composition of the coating.The UV-visible absorption spectrum of the complex formed in the electrodeposited solution with different additives was analyzed by a UV-Vis-NIR spectrophotometer.Results indicated that in Ch Cl-Gl A,the electrodeposition of copper involved two steps of oxidation-reduction with the first step of Cu2+→ Cu+and the second step of Cu+→Cu.All three additives promoted the deposition of copper in Ch Cl-Gl A,and ascorbic acid had the best effect,which could obtain a copper coating with good performance at room temperature.The electrodeposition of copper in Ch Cl-Gl A followed a three-dimensional instantaneous nucleation process and was an irreversible reaction controlled by diffusion.Moreover,the diffusion coefficients of Cu2+and Cu+could reach 4.003 9×10-7 cm2/s,4.762 7×10-7 cm2/s,respectively.The copper crystal prepared with ascorbic acid as additive was a polygonal sheet-like structure with distinct grains,and the optimal crystal plane was the(111)crystal plane.Besides,the average grain sizes of the copper layer with ad-ditives DTPA,EDTA-2Na and C6H8O6 were 50.71,55.12 and 52.73 nm.The average grain size of the copper layer without additive was 44.73 nm.
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