SURFACE STRUCTURAL AND CHEMICAL CHARACTERIZATION OF PT RU COMPOSITE ELECTRODES - A COMBINED STUDY BY XPS, STM AND IR SPECTROSCOPY/

Electrochemical Ru deposits on Pt(111) surfaces are investigated by ST M; the images of the Ru-modified surfaces show islands of monoatomic h eight and between 2-5 nm in diameter. The density of islands on the su rface depends on the Ru deposition potential (observed by STM and XRSD ) and the cyclic voltammograms indicate an increasing Ru coverage for lower deposition potentials. The Ru surface coverage is determined by ex-situ XPS measurements and a linear dependence of the Ru coverage on the deposition potential is demonstrated. IR spectra of a monolayer o f adsorbed CO on the Ru-modified Pt(111) surfaces show distinct bands for CO adsorbed on Pt and on Ru. For the integrated band intensity of the CO/Ru vibration a linear dependence on deposition potential is fou nd indicating that lateral dipole interactions between CO adsorbed on Pt and Ru are unimportant and that the CO coverage on the Ru islands i s constant for the Ru coverages investigated. The possibility of using adsorbate vibrational bands for the determination of the coverage of deposits is discussed.