Spontaneous Deposition of Sn/Pd on Au(111).

L.A. MEIER; S.G. GARCÍA; D.R. SALINAS

Sevilla, España

Congreso; 59th Annual Meeting of the International Society of Electrochemistry; 2008

International Society of Electrochemistry

The deposition of metal adlayers onto a foreign metal surface is one of the most extensively studied subjects in surface electrochemistry. It is well known that some of these bimetallic surfaces have electrocatalytic or catalytic properties better than those of the pure components [1]. In some cases the formation of these ultrathin layers can be achieved by "spontaneous deposition" using the so-called immersion technique [2] which deals with the reduction as well as the oxidation of metal adspecies that has been introduced spontaneously onto the electrode surface at open circuit from solutions containing the metal ions.In this work the spontaneous deposition of Sn onto Au(111) electrodes was studied by conventional electrochemical techniques and Scanning Tunneling  Microscopy (STM). The adsorption of Sn was carried out by immersing the gold single crystal in a Sn(II) containing solution at open circuit causing the spontaneous deposition of the tin species. This Au(111)/Sn modified surface was analysed in a sulphuric acid solution by cyclic voltammetry. These experiments showed typical anodic peaks which can be related to the dissolution of Sn adspecies [3].The in-situ STM images of the Au(111)/Sn modified surface showed flat terraces with rounded edges and two dimensional islands. The anodic polarization of this modified surface produced the gradual dissolution of the Sn adlayer which was evidenced by the formation of many holes and little islands on the terraces. In addition, at relatively high potentials another dissolution process was also observed, which affected principally the step edges. This effect could be related to the dissolution of a Au-Sn surface alloy phase.In addition, the subsequent immersion of the previously characterized Au(111)/Sn modified surface in a solution containing Pd(II) species promoted the spontaneous deposition of Pd. This phenomenon produced changes in the voltammetric spectra and this behaviour was correlated with the morphological changes observed in the STM images.REFERENCES[1]  N.M. Marković and P.N. Ross Jr., Surf. Sci. Rep. 45 (2002) 117.[2]  M.M.P. Janssen and J. Moolhuysen, Electrochim. Acta 21 (1976) 861.[3]  A. Rodes, J.M. Feliu, A. Aldaz, J. Clavilier,  J. Electroanal. Chem. 256 (1988) 455.