Surface chemistry of ketene on Ru(001). I: Surface structures

Ketene (CH sub 2 CO) adsorption and reaction on Ru(001) were studied by high-resolution electron energy loss spectroscopy (HREELS), static secondary ion mass spectrometry (SSIMS), and temperature programmed desorption (TPD). Only hydrogen, carbon monoxide, and CO sub 2 are observed in TPD. At 105K, low ketene exposures dissociate to CO and methylene and adsorb molecularly as an eta exp 3 (C,C,O) species. At higher exposures ketene adsorbs molecularly as eta exp 2 (C,C). Above 200K, adsorbed ketene hydrogenates to two distinct acyl species: eta exp 2 (C,O) acetaldehyde (CH sub 3 CHO), and eta exp 2 (C,O) acetyl (CH sub 3 CO). Adsorbed acetate is also considered. The H required for hydrogenation is supplied from decomposition of CH sub 2 and ketene. Above 200K, ethylidyne (CCH sub 3 ) is formed. Methylidyne (CH) and acetylide (CCH) are formed by decomposition of all the above oxygenate and hydrocarbon species. Dosing ketene on Ru(001) at 350K, where CO accumulates, favors ethylidyne formation. The adsorbed CO stabilizes ethylidyne, which otherwise decomposes at 320K. Dosing at 400K, which is above the threshold of CO desorption, results in CH and CCH. 55 ref.--AA