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Title: Adsorption of carbon monoxide on small aluminum oxide clusters: Role of the local atomic environment and charge state on the oxidation of the CO molecule

We present extensive density functional theory (DFT) calculations dedicated to analyze the adsorption behavior of CO molecules on small Al{sub x}O{sub y}{sup ±} clusters. Following the experimental results of Johnson et al. [J. Phys. Chem. A 112, 4732 (2008)], we consider structures having the bulk composition Al{sub 2}O{sub 3}, as well as smaller Al{sub 2}O{sub 2} and Al{sub 2}O units. Our electron affinity and total energy calculations are consistent with aluminum oxide clusters having two-dimensional rhombus-like structures. In addition, interconversion energy barriers between two- and one-dimensional atomic arrays are of the order of 1 eV, thus clearly defining the preferred isomers. Single CO adsorption on our charged Al{sub x}O{sub y}{sup ±} clusters exhibits, in general, spontaneous oxygen transfer events leading to the production of CO{sub 2} in line with the experimental data. However, CO can also bind to both Al and O atoms of the clusters forming aluminum oxide complexes with a CO{sub 2} subunit. The vibrational spectra of Al{sub x}O{sub y} + CO{sub 2} provides well defined finger prints that may allow the identification of specific isomers. The Al{sub x}O{sub y}{sup +} clusters are more reactive than the anionic species and the final Al{sub 2}O{sup +} + CO reactionmore » can result in the production of atomic Al and carbon dioxide as observed from experiments. We underline the crucial role played by the local atomic environment, charge density distribution, and spin-multiplicity on the oxidation behavior of CO molecules. Finally, we analyze the importance of coadsorption and finite temperature effects by performing DFT Born-Oppenheimer molecular dynamics. Our calculations show that CO oxidation on Al{sub x}O{sub y}{sup +} clusters can be also promoted by the binding of additional CO species at 300 K, revealing the existence of fragmentation processes in line with the ones experimentally inferred.« less
Authors:
;  [1]
  1. Instituto de Física “Manuel Sandoval Vallarta,” Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, 78000 San Luis Potosí, México (Mexico)
Publication Date:
OSTI Identifier:
22415567
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ADSORPTION; AFFINITY; ALUMINIUM OXIDES; BORN-OPPENHEIMER APPROXIMATION; CARBON DIOXIDE; CARBON MONOXIDE; CHARGE DENSITY; CHARGE STATES; DENSITY FUNCTIONAL METHOD; EV RANGE; ISOMERS; MOLECULAR DYNAMICS METHOD; MOLECULES; MULTIPLICITY; OXIDATION; OXYGEN; TEMPERATURE DEPENDENCE; YTTRIUM IONS