Comparative Study of the Electrodeposition Process of Tin on Copper Electrodes in Different Deep Eutectic Solvents

A.E. BOLZÁN; L.A. AZPEITIA; C.A. GERVASI

Prague

Congreso; 15- ISE Regional Meeting of the International Society of Electrochemistry; 2022

International Society of Electrochemistry

The electrodeposition process of tin on copper electrodes was studied in different deep eutectic solvents (DES). Electrolytes were prepared either from solutions of ethaline or reline, containing SnSO4 or SnCl2 or from a stoichiometric mixture of choline and tin chlorides. Experiments were carried out between 293 -- 353 K, by applying electrochemical techniques, scanning electron microscopy imaging and RDX analysis. Voltammetric profiles show significant differences both, in negative and in positive scans, mainly due to the proper response of the copper substrate in each DES. While it is possible to detect underpotential and overpotential electrodeposition processes in ethaline, in reline only the opd process is clearly observed. Current transients indicate for both, ethaline and reline, the occurrence of instantaneous nucleation and 3D growth under diffusion control of tin crystallites. The XRD spectra shows the formation of Cu3Sn and Sn5Cu6 intermetallic that prevails at short electrodeposition times. These species are produced by the slow diffusion of the tin into the copper lattice. As the thickness of the Sn film increases, the relative contribution of the intermetallics decreases. Impedance spectra contain two capacitive time constants at low overpotentials and a capacitive time constant and a Warburg contribution at high overpotentials. Diffusion coefficients of Sn(II) ions in the different DES were determined from Levich plots derived from rotating disc electrode runs at different temperatures. From the corresponding Arrhenius plots, the diffusion activation energies were calculated. Variations in Sn-deposit morphology obtained at different potentials, times, temperatures and solvent compositions were determined from SEM imaging.