Size-Dependent Carbon Monoxide Adsorption on Neutral Gold Clusters

Abstract

We report on experiments probing the reactivity of neutral Au(n) clusters, n = 9-68, with carbon monoxide. The gold clusters are produced in a pulsed laser vaporization cluster source, operated at room temperature (RT) or at liquid-nitrogen temperature (LNT), pass through a low-pressure reaction cell containing CO gas, and are subsequently laser ionized. The reaction probabilities are determined by recording mass abundance spectra with time-of-flight mass spectrometry. The main observations are a strong temperature dependence and a remarkable size dependence. Upon cooling of the cluster source to LNT, the reactivity increases substantially. At LNT, the reaction probabilities for Au(n) with the first CO molecule are about a factor 10 higher than at RT. Moreover, adsorption of two, three, and even four CO molecules is observed, in contrast to RT clusters which at most adsorb one CO molecule. This temperature dependence is related to the lifetime of the cluster-molecule complexes, being much longer for cold clusters. The observed striking size dependence is similar at both temperatures and is discussed in terms of the electronic structure effects.

The adsorption of CO on transition metal clusters: A case study of cluster surface chemistry

“…Later work by Anderson, Rosén, and coworkers identified rather smooth changes of the reactivity of V, Nb, Ni, and Rh clusters with size [31][32][33] and found more pronounced variations for Cu and Au clusters [34,35]. Higher sticking probabilities point to an increased complex stability and might be related to electronic shell closures for particular complex sizes (see below).…”

Gas phase chemistry of neutral metal clusters: Distribution, reactivity and catalysis

“…CO oxidation is also important in other areas such as respiratory protection and fuel gas cleanup. Gold based catalysts are employed for low temperature CO oxidation [121], and have been studied extensively in the condensed phase [122][123][124][125][126][127][128][129] and in the gas phase [130][131][132][133][134], but a search for alternative, low-cost, and noble metal free materials has led to the study of transition metal and metal oxide catalysts [135][136][137][138] for such reactions. In the following we present three studies dealing with the oxidation reactions of CO catalyzed by neutral gold clusters, iron oxide, and cobalt oxide clusters.…”

A theoretical study of CO adsorption on gold by Hückel theory and density functional theory calculations

“…[36] As CO is normally adsorbed on the top site, [28,29] it is predicted by Hü ckel theory that these doping metals (Ag, Cu, and Y) will weaken the CO adsorption. It have been proven that the CO adsorption on doped gold cluster by Ag, Cu, and Y actually is weaker than that on pure gold cluster by the experimental [37,38] or theoretical [39][40][41] studies.…”