Copper underpotential deposition at gold surfaces in contact with a deep eutectic solvent: new insights

Copper electrodeposition on polycrystalline gold electrode and on Au(hkl) single crystals was investigated in a deep eutectic solvent (DES). The employed DES consisted on a mix of choline chloride and urea (1:2). The interface Au(hkl) /DES was studied by using cycling voltammetry in the capacitive region. The blank voltammograms showed characteristic features, not previously reported, that demonstrates the surface sensitivity of this solvent. Afterwards, copper electrodeposition was analyzed, finding that it takes place through the formation of a UPD adlayer, evidencing the surface sensitivity of the phenomena. Voltammetric profiles showed similarities with those obtained in aqueous solutions containing chloride, suggesting that the copper UPD in this DES is strongly influenced by the presence of chloride