J.R.B. Gomes & F.Illas

CIQ/Departamento de Química da FCUP, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal and CERQT/Departament de Quimica Fisica, Universitat de Barcelona, C/ Marti i Franques, 1, E-08028 Barcelona

The interaction of metals with metal oxide surfaces is at the hearth of several relevant technologies. Among others, pertinent examples involve applications to metal-ceramic-based gas sensors, microelectronic devices and oxide-supported transition metal catalysts [1]. Therefore, it is not surprising that the physics and chemistry of the metal-oxide interface is being strongly investigated [2,3]. Several experimental studies concerning adsorption of metal atoms on oxide supports have been reported on the past few years. Unfortunately, the complexity of these systems makes it difficult to obtain direct, structural or electronic, information even under ultra-high vacuum, well-defined, controlled, experimental conditions. In some cases, the oxide surface structure is rather simple, i.e. MgO(100), although even in this simple case the surface presents a large concentration of vacancies and other point defects [4]. On the other hand, the alpha-Al2O3(0001) surface provides a paradigm of a complex surface which structure is still a matter of discussion [5]. The interaction of metal atoms with the alpha-Al2O3(0001) surface involves a higher degree of complexity not exempt of contradictory interpretations. Therefore, more insight into the interaction of metal atoms with this oxide is needed. For that reason, the cluster approach combined with the B3LYP method, DFT based, were used to study the adsorption of palladium atoms and palladium aggregates on the alpha-Al2O3(0001) surface. In this communication it will be presented a detailed study about the interaction of palladium atoms with the alpha-Al2O3(0001) surface, either resulting from cluster or 2D periodic computations. Results are compared with experiment when possible. Also, in this communication we will present results from cluster calculations, again at the B3LYP level of theory, of the interaction of small palladium clusters with the metal-oxide substrate. Some examples of industrial interesting reactions taking place on the metal/metal oxide interface will be presented.

[1]-C. R. Henry, Surf. Sci. Rep. 31 (1998) 231.

[2]-B. C. Gates, Chem. Rev. 95 (1995) 511.

[3]-D. W. Goodman, Chem. Rev. 95 (1995) 523.

[4]-G. Pacchioni in "The Chemical Physics of Solid Surfaces", Vol. 9., D. P. Woodruff, Ed., Elsevier, Amsterdam, (2001).

[5]- J. R. B. Gomes, I. de P. R. Moreira, P. Reinhardt, A. Wander, B. G. Searle, N. M. Harrison and F.Illas, Chem. Phys. Lett., submitted.