Eur. Phys. J. D (2013) 67: 35
https://doi.org/10.1140/epjd/e2012-30493-5

Regular Article

CO oxidation by copper cluster anions^*

¹ East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan
² Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
³ Cluster Research Laboratory, Toyota Technological Institute: in East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan

Received: 8 August 2012
Received in final form: 28 November 2012
Published online: 6 March 2013

Abstract

Reactions of CO and O₂ on size-selected copper cluster anions, Cu_n^- (n = 4–11), have been investigated at the collision energy of 0.2 eV by use of a guided ion beam-tandem mass spectrometer. Oxygen-adsorbed copper anions, Cu_nO₂^-, in particular Cu₅O₂^- and Cu₉O₂^-, show an evidence of the CO oxidation, that is, the formation of the monoxide Cu_nO⁻. The density functional theory calculation reveals that the CO oxidation occurs more exothermically on Cu₅O₂^- and Cu₉O₂^- than the other clusters. This can be explained by the relatively small dissociation energy of their Cu–O bonds. In addition, the calculations on Cu₅O₂^+/- indicate that the CO oxidation proceeds via a low-energy pathway for the anion owing to the structural rearrangement of the copper cluster compared to the cation.