For two types of sites

The adsorption energies (Eads) of the various species in reactions (1) - (4) are essential information for understanding methanol oxidation. The results are collected in Table 6, together with available experimental data. Calculations were done for two types of sites, on-top (t) and threefold hollow (h). Excepting H and OH, the species treated prefer the on-top site in both pure and mixed clusters. 

Assuming competitive adsorption of CO and H2 and surface reaction as the controlling step, compare the shapes of the predicted and experimental curves of r versus coif the surface is not uniform, could allowing for two types of sites give a better fit for this data in the region of nearly zero-order behavior ... 

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