| AVS 60th International Symposium and Exhibition | |
| Surface Science | Tuesday Sessions |
| Session SS-TuA |
| Session: | Metals and Alloys: Structure, Reactivity & Catalysis |
| Presenter: | D.A. Chen, University of South Carolina |
| Authors: | D.A. Chen, University of South Carolina R.P. Galhenage, University of South Carolina H. Yan, University of South Carolina K. Xie, University of South Carolina A.S. Duke, University of South Carolina |
| Correspondent: | Click to Email |
The nucleation, growth and surface composition of Pt-Co and Pt-Re bimetallic clusters on TiO2(110) have been investigated as model systems for understanding how surface chemistry can be controlled by bimetallic composition and interactions between the clusters and the oxide support. Scanning tunneling microscopy studies demonstrate that bimetallic clusters can be formed from sequential deposition of the metals when the metal with the lower mobility on titania (Co or Re) is deposited first to serve as nucleation sites for Pt. For the Co-Pt clusters, the surface composition is slightly Pt-rich compared to the bulk, despite the lower surface free energy for Co compared to Pt. While Co-Pt clusters have similar surface compositions regardless of the order of deposition, the inter-diffusion of metals in Re-Pt clusters is inhibited when Pt is deposited on top of Re; for the reverse order of deposition, XPS data indicate that a Re-Pt alloy is formed. Temperature programmed desorption experiments with CO show that CO adsorbs at both Co and Pt sites on the bimetallic clusters. Methanol decomposition chemistry has also been studied as a function of changing bimetallic cluster composition. Methanol decomposition produces CO and hydrogen as the main products on both pure Pt and pure Co clusters. On the bimetallic Co-Pt clusters, the selectivity for methane production increases, and the desorption of H2 at higher temperatures suggests that the intermediates have greater thermal stability.