CO-promoted formation of the alkali-oxygen bond on Ni(111).
High-resolution electron energy loss spectroscopy was used to study the coadsorption of alkali metals (Na, K) and oxygen on clean and CO-modified Ni(111) surfaces. We unambiguously show that on an alkali-precovered surface, the alkali-O bond was not formed upon O(2) exposure. On the contrary, the alkali-O bond was readily observed by exposing to O(2) the Ni(111) surface precovered with an alkali+CO phase. This enhanced oxidation rate of alkali metals in the presence of CO molecules was ascribed to the short-range CO-induced modification of the electronic charge of alkali-metal adatoms.
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Dipartimento di Fisica, Università degli Studi della Calabria, via ponte Bucci, 87036 Rende (Cs), Italy.
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