The Influence of Surface Defects on Adsorption Phenomena

Over the last decade, there has been considerable inte rest on the chemistry of methanol on transition metal surfaces, inspired in part by the use of copper as a catalyst in methanol synthesis.^1-4 The adsorption and decomposition of methanol have been investigated on a variety of surfaces for example, Ag(110, 111), Au(110), Cu(100, 110, 111), Pt(100, 110), Ni(100, 110, 111). In all surfaces the dominant surface intermediate is the methoxy radical that is easily formed by cleavage of O-H bond of methanol. Unfortunately, experimental data allow conflicting interpretations in what concerns the orientation of the methoxy radical on the surface. Theoretical work is required to clarify the local interaction of methoxy with the surface and the reaction mechanisms where it takes part.

In this communication, DFT calculations (with Becke3LYP hybrid method) of adsorption properties of atomic hydrogen and methoxy radical⁵ on different M_n clusters of the M(111) surface, with M= copper, silver and gold, are reported. The influence of defects on the metallic surface on the adsorption energy of H and CH₃O is discussed.

We thank JNICT and PRAXIS XXI for financial support.

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3. - I. E. Wachs e R. Madix, J. Catal. 53 (1978) 208.
4. - H. E. Dastoor, P. Gardner e D. A. King, Chem. Phys. Lett. 209 (1993) 493.
5. - J. R. B. Gomes and J. A. N. F. Gomes, submitted.

J.R.B. Gomes and J.A.N.F. Gomes

CEQUP/Faculdade de Ci�ncias da Universidade do Porto

Rua do Campo Alegre, 687

4150 Porto - Portugal

email: jrgomes and [email protected]