The interaction of CO and Li at a Ru(0 0 1) surface—a thermal desorption study

The interaction of carbon monoxide with the alkali metal lithium is studied on the single crystal substrate ruthenium surface Ru(0 0 1). The exceptionally strong interaction between CO and Li is investigated under various CO and Li coverages. Temperature programmed desorption spectroscopy shows the shift of the low coverage CO desorption peak (θCO<0.05) from its initial desorption temperature at 520–840 K when the lithium coverage is increased from zero to 1/3 of a mono-layer. Above that, the CO desorption temperature does no longer shift, but the desorption is concentrated in a single sharp Li/CO codesorption feature. Even stronger interaction of CO and Li is seen on a gold covered Ru surface (Au/Ru(0 0 1)). Au blocks the adsorption of CO. In the presence of Li however CO adsorbs readily. The uptake is roughly half that of the bare Ru surface and the thermal desorption occurs only above 900 K with the strong codesorption feature of Li and CO at 1080 K. The formation of a Au/Li alloy on the Ru substrate is confirmed.