Strongly cluster size dependent reaction behavior of CO with O2 on free silver cluster anions

Socaciu, Liana D.; Hagen, Jan; Roux, Jean-Michel; Popolan, Denisia; Bernhardt, Thorsten M.; Wöste, L.; Vajda, Štefan

doi:10.1063/1.1644103

Cited by 105 publications

(99 citation statements)

References 27 publications

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“…It has been recognized that the cluster alone cannot break the O-O bond, but because of cooperative effects the oxidation reaction might proceed (7,16 (17). In both cases structural and energetic properties of these gold and silver oxides are very similar.…”

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confidence: 72%

Reactivity-promoting criterion based on internal vibrational energy redistribution

Mitrić

B̈rgel

Bonaić-Koutecký

2007

Proc. Natl. Acad. Sci. U.S.A.

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We propose to introduce intrinsic dynamical properties as a criterion for promoting reactivity of small size noble metal reactive centers relevant for heterogeneous catalysis. To illustrate the concept, collisions between Ag 6 ؊ or Au 6 ؊ clusters and molecular oxygen have been investigated with direct ab initio molecular dynamics by using DFT. We show that different nature and efficiency of internal vibrational energy redistribution (IVR) during reaction dynamics is responsible for significantly different sticking probabilities of O2 to gold and to silver clusters. Small nanoparticles and clusters exhibit surprising new chemical and physical properties because of size and structure selective quantum confinement. In such a nonscalable size regime in which ''each atom counts,'' by adding or removing a single atom, the properties of clusters can be tuned to achieve desired functionality. A prominent example is the unexpected finding that small, nanosized gold particles can catalyze oxidation reactions occurring in, e.g., combustion (1-5). Also, silver is widely used as a catalyst in important industrial processes such as epoxidation (5). In both cases, mechanisms responsible for oxidation reactions are required for the rational design of efficient nanocatalysts, but they remain to be unravelled.Until now, studies (3, 4, 6-13) of the size-dependent reactivity of small gold and silver clusters in the gas phase or on supports have been focused on establishing relationships between structure, charge, and reactivity based on energetics, which is a very important aspect (6). However, dynamical processes such as nature and timescale of the internal vibrational energy redistribution (IVR) between interacting subunits during the reaction have not yet been considered.Here, we wish to introduce the dynamical aspect as a reactivity promoting criterion. We will show that resonant IVR between reactants promotes reactivity toward adsorbates in contrast to dissipative IVR, which prevents reactions. This will be illustrated with anionic gold versus silver clusters reacting with molecular oxygen as examples. Although the influence of an interface plays an important role, the gas phase study allows a clear conceptual framework for examination of dynamical aspects. We first briefly describe previous findings and then address new aspects involving dynamical properties.From the electronic and structural size-dependent properties of anionic gold and silver clusters, an understanding of the binding toward molecular oxygen has been gained (4,7,10,13,14). An even/odd alternation of binding energies has been found for adsorption of O 2 onto small anionic gold (9, 11, 15) and silver clusters (9, 13). Clusters with an odd number of electrons strongly bind O 2 , which is one-electron acceptor. Also, electron affinities of coinage metals exhibit an even/odd alternation (9). Therefore, the anionic noble metal clusters with an even number of electrons (odd number of atoms) are inert toward O 2 . Because O 2 acts as a one-electron acceptor, these...

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confidence: 72%

Reactivity-promoting criterion based on internal vibrational energy redistribution

Mitrić

B̈rgel

Bonaić-Koutecký

2007

Proc. Natl. Acad. Sci. U.S.A.

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“…In contrast, small negatively charged silver clusters exhibit no reactivity toward CO at all. 4,12,13 A thermal catalytic CO oxidation mechanism employing molecular oxygen was shown to proceed on free Au 2 − .…”

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confidence: 99%

“…to cooperatively coadsorb O 2 and CO to be active oxidation catalysts in the CO combustion reaction. 4 Nothing is known so far about the capabilities of free silver cluster cations to promote the CO oxidation reaction.…”

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confidence: 99%

“…1 However, in contrast to highly dispersed gold metal particles on oxide supports and free gas-phase gold clusters, which have attracted considerable interest in recent years, 2 much less is known about oxidation reactions catalyzed by silver clusters. 3,4 Therefore, a comparative study of the CO oxidation capabilities of free gold and silver trimer cations was performed here.…”

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confidence: 99%

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Communication: CO oxidation by silver and gold cluster cations: Identification of different active oxygen species

Popolan

Bernhardt

2011

The Journal of Chemical Physics

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“…Importantly, in this case, support effects do not contribute to the picture, giving an opportunity to focus on the properties of the isolated nanoparticles. Several research groups have studied metal clusters in the gas phase and have pinpointed the extremely strong dependence of reactivity of ultrasmall clusters on their size (Figure 9.2a) [35][36][37][38][39][40]. This is an excellent example of pure electronic size effects with a strong correlation between the trends in reactivity of clusters and their electronic properties (Figure 9.2b) unaffected by the presence of a support or organic ligands and capping agents.…”

Section: Size Effects -Setting the Scenementioning

confidence: 99%

Tailored Nanoparticles for Clean Technology–Achieving Size and Shape Control

Golovko

2013

Heterogeneous Catalysts for Clean Technology

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Strongly cluster size dependent reaction behavior of CO with O2 on free silver cluster anions

Cited by 105 publications

References 27 publications

Reactivity-promoting criterion based on internal vibrational energy redistribution

Reactivity-promoting criterion based on internal vibrational energy redistribution

Communication: CO oxidation by silver and gold cluster cations: Identification of different active oxygen species

Tailored Nanoparticles for Clean Technology–Achieving Size and Shape Control

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