Formation of Au/Pd-Sn trimetallic particles onto vitreous carbon by electrochemical deposition

L.A. MEIER; S.G. GARCÍA; D.R. SALINAS

Nice, Francia

Congreso; The 61st Annual Meeting of the International Society of Electrochemistry; 2010

International Society of Electrochemistry

The formation of bimetallic or trimetallic particles distributed onto a conductor substrate is a way to obtain superficially modified electrodes that may have electrocatalytic properties for some reactions of technological interest. This is the case of the Au-Pd-Sn trimetallic system, which presents interesting properties for the electroreduction of nitrate ions.The aim of this work is the formation of Au/Pd/Sn trimetallic system onto vitreous carbon (VC). We study the sequential deposition process of Pd and Sn on Au microcrystals, previously electrodeposited onto VC. The sequential depositions were performed by immersing the VC/Au modified substrate in solutions containing the respective ions, favouring the initial adsorption of PdCl42- ions in the Pd case or the spontaneous deposition of Sn0 through a disproportionation reaction. In Pd case, were subsequently applied specific polarization routines to ensure the metal reduction.The presence of Pd, Sn and the binary system Pd-Sn onto the VC/Au substrate was characterized by cyclic voltammetry and Auger electron spectroscopy (AES). The results show that the deposition of Pd and Sn is selective on the Au microcrystals present on VC, due to the strong interaction energy between the three metals. The voltammetric studies have shown the existence of Sn on the VC/Au/Pd modified substrate, being present on the surface of Pd, probably forming a core-shell structure or alloy. This can be deduced from the presence of characteristic peaks in the cyclic voltamogramm, that are in agreement with those obtained during the oxidation of the modified electrodes Au(polycrystalline)/Sn [1], Au(111)/Sn [2] y Au(111)/Pd/Sn [3]. During this oxidation process, the Sn present is removed, exposing the Pd surface, showing the typical voltammetric response of the system VC/Au/Pd.The XPS measurements showed the presence of Pd and Sn. The results indicate a higher concentration of Sn on the outside of the metallic deposit, which tends to decrease in depth, the opposite occurs with the Pd. The Au presence is not detected on the surface and its concentration tends to increase gradually, according to the bombardment time, indicating that the deposition of Pd and Sn is selectiveReferences[1] A. Rodes, J.M. Feliu, A. Aldaz, J. Clavilier, J. Electroanal. Chem. 256 (1988) 455.[2] L.A. Meier, D.R. Salinas, J.M. Feliu, S.G. García, Electrochem. Comm. 10 (2008) 1583.[3] L.A. Meier, Tesis Doctoral, UNS (2010).