EX-SITU TDS INVESTIGATION OF CARBON-MONOXIDE ELECTROSORBED ON POLYCRYSTALLINE PLATINUM

A polycrystalline platinum electrode covered with various amounts of e lectrosorbed carbon monoxide was transfered to ultrahigh vacuum for in vestigation by thermal desorption spectroscopy (TDS). Solution dosing yielded a saturation coverage up to 15% higher than that obtained by g as phase dosing at room temperature. The thermal desorption features f or electrosorbed and gas-phase-dosed carbon monoxide are similar for s aturated layers. Submonolayer coverages, obtained by partial oxidation as well as by emersion during steady state carbon monoxide electro-ox idation, show thermal desorption features indicating an island structu re with high carbon monoxide concentration. No electrolyte residues we re found for emersed saturated carbon monoxide layers, but water and s ulfate thermal desorption signals increase with decreasing carbon mono xide coverage. Coadsorbed oxygen was found at low carbon monoxide cove rages when the electrode was emersed during steady state carbon monoxi de electro-oxidation near 900 mV/RHE.