Galvanic Displacement Deposition of Bismuth on Copper in the Ambient Ethaline Deep Eutectic Solvent in the Absence and Presence of Water and Additives

A facile approach of forming bismuth (Bi) films on copper (Cu) substrates via galvanic displacement using the deep eutectic solvent (DES) Ethaline (choline chloride-ethylene glycol; ChCl-EG) as the reaction medium was studied. Electronic absorption spectra and cyclic voltammetric behavior implied that Cu atoms were displaced by Bi atoms via the consumption of Bi(III) complex ions and the formation of Cu(I) species; the latter was oxidized to Cu(II) under ambient air. It is evident that the concentration of Bi(III) in Ethaline as well as the reaction temperature affect the surface morphologies and crystallization of the formed Bi layers, which follows the conventional behavior of nucleation and growth similar to the electrodeposition. Water content in the Ethaline DES seemed to promote the galvanic displacement by decreasing the solution viscosity, and enhancing the mass transport rate of the reacting species. Additives such as cetyltrimethylammonium bromide (CTAB), and molecular thiourea (TU) showed significant effects on the surface morphologies of the Bi layers. (C) 2019 The Electrochemical Society.