We have studied with DFT supercell calculations the role of the charge and of the MgO support in the activation of O2 by a Au5 cluster. We considered gas-phase Au5 and Au5- clusters and Au5 deposited on a stepped MgO surface and on the same surface in the presence of a specific defect, a (H+)(e-) center. On this center, Au5 forms a stable Au5- supported species. O2 activation depends on the charge state of the gold cluster, but this is not a sufficient condition. In fact, it is only on Au5-/MgO that O2 becomes activated (superoxo species). The reason is that O2- is bound at the interface between Au5 and the oxide and benefits from the interaction with the ionic support, an effect which is missing on free Au5-. The activation of the O-O bond on supported anionic gold clusters does not result in a substantial reduction of the dissociation barrier which remains about 2 eV. The implications for low-temperature CO oxidation on very small Au clusters are discussed. © 2010 American Chemical Society.
Roldan, A., Ricart, J., Illas, F., Pacchioni, G. (2010). O-2 Activation by Au-5 Clusters Stabilized on Clean and Electron-Rich MgO Stepped Surfaces. JOURNAL OF PHYSICAL CHEMISTRY. C, 114(40), 16973-16978 [10.1021/jp1017357].
O-2 Activation by Au-5 Clusters Stabilized on Clean and Electron-Rich MgO Stepped Surfaces
PACCHIONI, GIANFRANCO
2010
Abstract
We have studied with DFT supercell calculations the role of the charge and of the MgO support in the activation of O2 by a Au5 cluster. We considered gas-phase Au5 and Au5- clusters and Au5 deposited on a stepped MgO surface and on the same surface in the presence of a specific defect, a (H+)(e-) center. On this center, Au5 forms a stable Au5- supported species. O2 activation depends on the charge state of the gold cluster, but this is not a sufficient condition. In fact, it is only on Au5-/MgO that O2 becomes activated (superoxo species). The reason is that O2- is bound at the interface between Au5 and the oxide and benefits from the interaction with the ionic support, an effect which is missing on free Au5-. The activation of the O-O bond on supported anionic gold clusters does not result in a substantial reduction of the dissociation barrier which remains about 2 eV. The implications for low-temperature CO oxidation on very small Au clusters are discussed. © 2010 American Chemical Society.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.