Surface interaction between H/sub 2/ and Co/sub 2/ on Rh/Al/sub 2/O/sub 3/, studied by adsorption and infrared spectroscopic measurements

Adsorption studies of hydrogen or carbon dioxide on alumina-supported 5% rhodium with or without preadsorbed hydrogen indicated that the presence of hydrogen enhanced the carbon dioxide adsorption by a reaction which formed carbon monoxide and water and by formation of a surface complex. IR spectroscopy revealed the formation of a formate surface species whose apparent activation energy, calculated from the temperature-dependence of its formation, was 4.2 kcal/mole. Literature data for 20 kcal/mole activation energy of formate formation on alumina indicated the promotional effect of rhodium on the reaction of hydrogen with carbon dioxide. The surface reactions are discussed.