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Keywords:

Science & Technology, Physical Sciences, Chemistry, Physical, Physics, Atomic, Molecular & Chemical, Chemistry, Physics, DEPENDENT REACTION-KINETICS, BINDING-ENERGIES, CO ADSORPTION, BIMETALLIC CLUSTERS, N CLUSTERS, SIZE, SILVER, O-2, CATALYSIS, OXIDATION, 02 Physical Sciences, 03 Chemical Sciences, 09 Engineering, Chemical Physics, 34 Chemical sciences, 40 Engineering, 51 Physical sciences

Abstract:

The effect of a single vanadium dopant atom on the reactivity of small gold clusters is studied in the gas phase. In particular we investigated carbon monoxide adsorption on vanadium doped gold clusters using a low-pressure collision cell. Employing this technique the reactivity of both neutral and cationic clusters was studied under the same experimental conditions. Analysis of the kinetic data as a function of the pressure in the reaction cell shows that the reaction mechanism is composed of a fast adsorption and a delayed dissociation reaction. It is demonstrated that the reactivity of positively charged Au(n)V(m)(+) (n = 8-30, m = 0-3) is greatly enhanced as compared to the corresponding neutral species and that dissociation rates decrease with decreasing temperatures. While the overall magnitude of the reactivity does not change upon doping with vanadium clusters, the size dependence is significantly affected. The neutral singly vanadium doped gold clusters show a sudden drop after size Au(13)V, followed by a smooth increase, in contrast to the extended odd-even staggering for bare gold clusters. This difference can be explained by changes in the electronic structure of the clusters, related to the partly filled 3d shell of the vanadium dopant atom.