Characterization of platinum-rutheniun electrodeposits using XRD, AES and XPS analysis

Metallic deposits of platinum-ruthenium were produced on a gold substrate by electrodeposition from salts in platinum and ruthenium solutions. These deposits were characterized by X-ray diffraction, Auger electron spectroscopy and X-ray photoelectron spectroscopy. The XRD studies showed a crystalline alloy whose structure was cubic centered on the face; that is, an alloy of one phase as a substitutional solid solution where the platinum atoms were replaced by ruthenium atoms. Some deposits grew with the crystals oriented according to a preferential direction and developed a crystallographic texture. The XPS analysis revealed that, in principle, there are no compounds with oxidation states different from metal ruthenium and metal platinum. Good correlations were obtained between the values of the ratios in atomic composition of Pt-Ru for the different samples calculated for XPS and Auger spectroscopy. The catalytic activity of the electrodeposits was measured in methanol solutions. From the XRD studies, the network parameters and the crystallographic texture were compared before and after using them in electrochemical methanol oxidation, The distribution of the observed relative integrated intensities of the diffraction patterns of the deposits showed a variation which is more evident when the deposit has a preferential grain orientation. The reflective power of planes (111) decreases after methanol oxidation. (C) 1999 Published by Elsevier Science S.A. All rights reserved.