Abstract
This is a review of the replacement phenomena of chemisorbed gases on metal surfases.
The replacement phenomena are discussed by classifing into two groups.
The first group is “the simple mutual replacement”. In this group, the replacement phenomena are complicated at higher coverage. In the co-adsorption and/or the mutual replacement of H2 and CO, the surface species contained both H and CO are found, while in the simultaneous adsorption of H2 and CO, the LEED patterns of the adsorbed surface differ from these of the N2-covered surface or the CO-covered one. These results support that there is a strong interaction between the different kind adsorbates on the surface.
In the second group called “the reactive replacement”, the preadsorbed CO on the surface is replaced by oxygen subsequently adsorbed with reaction such as CO2 desorption. In the cases discussed, qualitatively the sequence of the replacement are explaned by the value of the heat of adsorption.
The nature of the replacement process will be clarified by the extensive studies including the adsorbate-adsorbate interaction.
