| AVS 58th Annual International Symposium and Exhibition | |
| Surface Science Division | Tuesday Sessions |
| Session SS1-TuM |
| Session: | Chemisorption & Surface Reactions |
| Presenter: | J. Adam Stephens, University of Texas at Austin |
| Authors: | J.A. Stephens, University of Texas at Austin H.C. Ham, University of Texas at Austin G.S. Hwang, University of Texas at Austin |
| Correspondent: | Click to Email |
Bimetallic materials have shown great promise for the development of superior catalysts. The recent surge of new interest in catalysis by gold has led researchers to investigate the effects of adding gold to other metals. While mechanisms underlying the alloying effect are still not understood in detail, recent evidence suggests that the enhanced reactivity of bimetallic catalysts can be attributed to a combination of metal-metal interactions (ligand effect) and unique mixed-metal surface sites (ensemble effect). The ability to accurately predict the arrangements of constituent atoms in a surface alloy is indispensable to unraveling the roles played by the ensemble and ligand effects in the performance of bimetallic model catalysts. We have developed a scheme to predict the equilibrium arrangement of atoms in surface alloys in the presence of adsorbates at finite temperatures. It is based on the Ising model and is capable of reproducing DFT-predicted total energies to within no more than a few meV per surface atom. We have used it successfully to predict the populations of monomers, dimers, and other, larger ensembles in Au-Pd and Au-Pt fcc (111) and (100) surface alloys. The scheme will be presented in detail, as well as what we have learned about the effects of temperature, composition, and the presence of adsorbates on ensemble formation in both fcc (111) and (100) surface alloys. We will also discuss how the atomic arrangements affect the reactivity of gold-based alloy surfaces, particularly towards oxygen reduction and carbon monoxide oxidation.