Electrodeposition of Tin-Reduced Graphene Oxide Composite from Deep Eutectic Solvents Based on Choline Chloride and Ethylene Glycol

Abstract

Some experimental results regarding the direct electrodeposition of tin-reduced graphene oxide composite (Sn-rGO) compared to the electrodeposition of tin metal (Sn) from a deep eutectic solvent (DES), namely using choline chloride-ethylene glycol eutectic mixtures, are presented. Raman spectroscopy demonstrated that GO is also reduced during the tin electrodeposition. Scanning electron microscopy (SEM) confirmed the presence of incorporated graphene related material in the composite film. X-ray diffraction patterns showed that the presence of rGO in the deposit diminished preferred orientation of Sn growth along the planes (101), (211), (301), and (112). The analysis of current-time transients involving Scharifker & Hills model has shown that Sn-rGO composite deposition process corresponds to a nucleation and tridimensional growth controlled by diffusion, with nucleation evolving from progressive to instantaneous upon increasing the overpotential. Diffusion coefficients at 25 °C of 9.4 × 10−7 cm2 s−1 for Sn(II) species in the absence and of 14.1 × 10−7 cm2 s−1 in the presence of GO, were determined. The corrosion performance has been assessed through the analysis of the recorded potentiodynamic polarization curves and of the electrochemical impedance spectra during continuous immersion in aerated 0.5 M NaCl aqueous solution at 25 °C for 144 h. A slight improvement of the corrosion performance in the case of the Sn-rGO composite coatings was noticed, as compared to pure Sn ones. Furthermore, the solderability performance has been evaluated. The solder joints showed a proper adhesion to the substrate with no fractures, and wetting angles around 44° have been determined, suggesting adequate solderability characteristics.