STUDIES OF CARBON-MONOXIDE AND HYDROGEN ADSORPTION ON NICKEL AND COBALT FOILS AIMED AT GAINING A BETTER INSIGHT INTO THE MECHANISM OF HYDROCARBON FORMATION

Systematic studies of adsorption of hydrogen and carbon monoxide on po lycrystalline surfaces of nickel and cobalt have been carried out. The aim of these studies was to pin a better insight into the catalyzed f ormation of hydrocarbons from H-2-CO mixtures. We have studied the ads orption of these gases by means of thermal desorption spectroscopy (TD S) on nickel foils and powders. More recently, we have obtained desorp tion spectra of hydrogen adsorbed on cobalt foils and powders. In this work we described desorption spectra of carbon monoxide on cobalt foi ls. Carbon monoxide desorption from cobalt foils was studied in a simi lar way as prior work, using a mass spectrometric method in an ultra h igh vacuum system. Two carbon monoxide desorption peaks were observed. These two states correspond to molecular CO and presumably dissociate d CO, as it is observed in the case of stepped surfaces of Ni and Co s ingle crystals. An activation energy of around 4.0 kcal/mol is obtaine d for the molecular state while for the dissociated state the energy i s coverage-dependent with a value between 8.0 and 15.0 kcal/mol. The c arbon monoxide desorption peaks were fitted with near Gaussian curves which facilitates the analysis of the data to obtain activation energi es for desorption. Kinetic parameters for carbon monoxide and hydrogen desorption from nickel and cobalt foils are provided and compared wit h already published data involving single crystals.