Underpotential deposition of cadmium onto Cu(111) and Cu(110) from chloride containing solutions

Underpotential deposition (UPD) of Cd onto the (111) and (110) faces of copper in chloride containing electrolyte has been investigated by cyclic voltammetry and the potentiostatic pulse technique. It was shown that the UPD of Cd onto the (111) face of copper is characterized by two pairs of peaks, one pair corresponding to the formation of the (√19 √ 19)R23.4º structure of Cd and the other one, taking place close to the reversible potential of Cd deposition, corresponding to the alloying of Cu with Cd. Deposition of (√19 √19)R23.4º structure of Cd was found to take place by the mechanism of replacement of the adsorbed structure of chloride, without chloride desorption (the chloride stays adsorbed on top of the Cd layer). Similar behaviour was found for the (110) face of copper, with more pronounced alloying which provokes an irreversible change of the original (110) surface of copper