REACTION OF LI WITH CO ON RU(001) AND AG RU(001) SUBSTRATES/

Lithium is found to behave quite differently from other alkali metals in its coadsorption with CO on transition metal substrates, and also i n its multilayer interaction with CO. Coadsorbed CO and Li on Ru(001) interact or react to give several chemically different species, which depend on surface stoichiometry and surface temperature. At low Li cov erage (< 1 ML) and 80 K a lithium-CO complex with stoichiometry Li(n)( CO)2n is formed and produces an extremely narrow CO desorption peak at 730 K corresponding to the reaction Li(n)(CO)2n(ad) --> Li(n)(CO)n(ad ) + n CO(g). CO adsorbs readily on multilayer Li surfaces at 80 K and forms a compound which is tentatively assigned the stoichiometry Li2n( CO)n. Annealing to 500 K desorbs the Li multilayer and transforms this compound to Li(n)(CO)n. The Li(n)(CO)n compound decomposes on the sur face with further heating to give a Li + CO codesorption TPD peak at 8 50 K, which is much higher than other alkali + CO codesorption peaks o n Ru(001). The Li-CO chemical interaction depends strongly on the subs trate chemical activity. Li-CO compounds form at lower Li coverage on Ag than on Ru, due to the weaker interaction of Ag with the adsorbates . in addition, a more strongly bound compound with TPD codesorption pe ak at 1020 K and stoichiometry Li(m)(CO)n, where n > m, is observed on Ag but not on Ru.