DIFT studies of CO adsorption and activation on some transition metal surfaces

The difference in adsorption for CO on the M(100) (M = Cu, Ag, Au, Pd, Pt) surfaces has been systematically investigated by first-principle density functional theory. The results indicate that the chemisorption of CO on these transition metal surfaces belongs to non-dissociative adsorption. The increased theoretical CO bond length of 0.1154 similar to 0.1161 nm (compared to 0.1128 nm in the gas phase) demonstrates the activation of the CO bond. We have carried out binding energy analysis, a natural bond orbital analysis and Mulliken population analysis of CO/M(100) adsorption systems. It can be concluded from the analyzed results that the adsorbability of CO decreases in the order of Pd (100), Pt (100), Cu (100), Ag (100) and Au (100). We have also discussed the implications of these results in terms of the catalysis of the water gas shift (WGS) reaction. From the volcano-shaped relationship between metal turnover number at 300 degreesC and binding energy of carbon monooxide and the electron transfer number of d orbital, it can be found that copper may be the optimum reactivity component of the catalyst in corresponding to the WGS reaction. Our calculations agree well with the experimental values and may explain the reason why copper is more activitive than other metals in a qualitative view.