| AVS 61st International Symposium & Exhibition | |
| Surface Science | Tuesday Sessions |
| Session SS-TuP |
| Session: | Surface Science Poster Session |
| Presenter: | Randima Galhenage, University of South Carolina |
| Authors: | R.P. Galhenage, University of South Carolina H. Yan, Brookhaven National Laboratory D.A. Chen, University of South Carolina |
| Correspondent: | Click to Email |
The study of metal clusters on single-crystal oxide supports has garnered much attention as model systems for fundamental investigations of surface activity that can guide the rational design of new catalyst. We have studied the growth and activity of monometallic and bimetallic clusters on TiO2(110) for metals such as Au, Co, Pt and Re, since these metals are known to have desirable properties for alcohol reforming and oxidation reactions. Scanning tunneling microscopy studies show that the cluster size and number of nucleation sites for these metals depend on the mobility of each metal on the titania surface. In general, the diffusion length decreases with increasing metal-titania bond strengths, and DFT studies show that the metal-titania bond strengths can be predicted directly from metal-oxygen bond strengths. Bimetallic clusters (Au-Co, Pt-Co, Pt-Re) were prepared from sequential deposition by growing the metal with the lower mobility first, followed by the more mobile metal. In general, exclusively bimetallic clusters are formed when the number of seed clusters generated from the deposition of the first metal provides a sufficient number of nucleation sites for the second metal. Surface compositions for the clusters were investigated by low energy ion scattering spectroscopy; for metals that do not alloy in the bulk, like Co and Au, core-shell structures are formed, and the surface composition is determined by the relative surface free energies. For metals that are bulk miscible, like Co-Pt and Pt-Re, both metals exist at the surface, regardless of the relative surface free energies. The chemical activity of the bimetallic clusters for CO adsorption and methanol reaction were investigated by temperature programmed desorption experiments. The addition of Au and Pt to Co clusters increased the thermal stability of the surface intermediate by inhibiting C-H bond scission and resulted in H2 and CO desorption at higher temperatures.