2015 Volume 56 Issue 4 Pages 479-484
Adsorption structure and electronic structure of ethylene on Pt3Ti(001) and PtTi3(001) intermetallic compounds surfaces are studied in terms of density functional calculations. In both intermetallic compounds, adsorption energy of bridge and hollow sites are larger than that of the atop sites. Moreover, obtained adsorption energy and the C-C separations at most sites on both intermetallic compounds are larger than those reported for Pt(111). Analyzing the surface LDOSs, it turns out that the bimodal density of states made by the occupied Pt d-states and unoccupied Ti d-states are effectively interact with the HOMO and LUMO of ethylene, which are bonding and anti-bonding states of the π-bond between carbon atoms, and then leading the elongated C-C bond and large adsorption energy. Larger adsorption energy at bridge and hollow sites is also understood in the same way. Although we found out the possibility that the bimodal density of states realized in intermetallic compounds composed of early and late transition metals is effective for molecular dissociation reaction generally, no clear evidence indicating the experimentally reported higher catalytic activity of Pt3Ti than PtTi3 and Pt in the ethylene hydrogenation is obtained in this study.