The Adsorption and Oxidation of Carbon Monoxide

The studies of Garner and his co-workers in the years 1928-1939, which had established the existence of two types of carbon monoxide and hydrogen chemisorption on oxides and which identified irreversible chemisorption with incipient reduction, were followed in the immediate postwar period by an intensive study of the properties of copper oxide (12-15). The work was later extended to nickel oxide (16) and cobalt oxide (17,18). With each of these oxides it was established that carbon monoxide was capable of reacting not only with lattice oxygen, but also with adsorbed oxygen. The concept of irreversible chemisorption involving a carbonate ion and ulti- 

We begin with a discussion of results obtained on copper (cuprous) oxide. Magnetic studies (20) have confirmed that the method of preparation yielded only cuprous oxide. On a surface free from adsorbed oxygen, carbon monoxide could be adsorbed reversibly at 20°. If, however, oxygen had been preadsorbed at 20°, the rapid adsorption of carbon monoxide 

In the light of these experiments with CO2 adsorption, it was of interest to see whether better agreement with the experimental heats of interaction could be obtained on the basis of a reaction leading to the CO3 complex rather than to C02(,j . The heat of adsorption of CO2 on to a preoxygenated surface was found to be 21 kcal./mole. Using, as before, the two other experimental heats of 55 and 20 kcal./mole for oxygen and for CO respectively on the baked-out surface, the heats to be expected for formation of the CO3 complex on copper oxide are readily calculated as follows 16)  

These heats are to be compared with the experimental values of 49 kcal. and 100 kcal. respectively. There is no improvement in the agreement for the CO heat, where the observed time dependence of the reactivity of adsorbed oxygen enters as a complication, but the oxygen heat is in very much better accord with the concept of CO3 complex formation. 

The surface reaction of carbon monoxide and oxygen on nickel oxide 16) and on cobalt oxide 17) was also investigated by the same method of 

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Lucas CA, Markovic NM, Ross NM. 1999. The adsorption and oxidation of carbon monoxide at the Pt(lll)/electiol3de interface atontic structure and surface relaxation. Surf Sci 425 L381-L386. 

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