(76a) Adsorption And Diffusion Of Transition Metal Clusters Over γ-Alumina

Authors: 
Deskins, N. A., Pacific Northwest National Laboratory
Dupuis, M., Pacific Northwest National Laboratory

γ-alumina (γ-Al2O3) supported transition metal catalysts are widely used in heterogeneous catalytic processes, including water-gas shift, hydrodesulfurization and NOx reduction. Current findings indicate that small metal clusters can form on the γ-alumina surface[1], and the nature and strength of interactions between the metal cluster(s) and γ-alumina play the key role in controlling the stabilities and geometrical structures of metal clusters and their catalytic activity. Despite the industrial importance of γ-alumina, atomic-level surface geometries have only been recently identified[2] due to the complex nature of the γ-alumina structure.  We have used this development to study the metal atom/γ-alumina interface.

Using density functional theory (DFT) we will compare the adsorption and diffusion of several transition metal atoms over the (111) γ-alumina surface, including Pt, Pd, Cu, Au, and Ag. We identify the stable adsorption sites by mapping the potential energy surface for metal adsorption. Analysis of the electronic structure provides further understanding of the bonding mechanism and degree of charge transfer. These results allow a comparison of the different metals and their affinity for the γ-alumina surface. Finally, we present modeling of the diffusion behavior of the metal atoms using a combination of DFT-calculated barriers and kinetic
Monte Carlo simulation.

This work was supported by the Laboratory Directed Research Development (LDRD) project at the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the Department of Energy.

[1]  Gates, B. C. Chem. Rev. 1995, 95, 511.

[2]  Pinto, H. P.; Nieminen, R. M.; Elliott, S. D. Physical Review B 2004, 70.