AUGER-ELECTRON SPECTROSCOPY, LOW-ENERGY-ELECTRON DIFFRACTION, AND ELECTROCHEMISTRY OF CARBON-MONOXIDE ON A PT(100) ELECTRODE

We report on carbon monoxide adsorption on the Pt(100) electrode in CO -saturated perchloric and sulfuric acid solutions studied by a combina tion of low-energy electron diffraction, Auger electron spectroscopy, and electrochemistry. We have developed an experimental method that pr oduces accurate CO coverages making use of a capacitive current genera ted due to iodine adsorption at a constant electrode potential. Using this method, we have obtained the saturation CO coverage equal to 0.77 +/- 0.04 ML, in a good agreement with the quantitative Auger electron spectroscopy result of 0.79 +/- 0.09 ML. The LEED analysis of the sat uration CO structure that corresponds to the 0.77 ML coverage gives ri se to the Pt(100)c(4X2) surface structure, as in earlier gas-phase stu dies of the equivalent surface system. We also present a complete Auge r electron spectroscopy characterization of the electrochemical CO ads orbate. The detailed spectroscopic data closely correspond to the prev iously reported spectral features for carbon monoxide adsorbed on rele vant catalytic substrates in the gas phase. We also specify conditions of a safe transfer of the CO-covered platinum electrode from solution to ultrahigh vacuum through which no desorption of CO takes place.