Exploration of multi-element clusters activating chemical bonds of small molecules for designing nano-materials by using vibrational spectroscopy

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The reactivities of metal clusters, metal oxide clusters and their complexes with small molecules such as N2O and CO were investigated by the experiments and theoretical studies. For neutral Rh clusters, they extract oxygen atom from N2O. The oxygen transfer reactions occur repeatedly, and the Rh oxide clusters were produced having a number of oxygen atoms in them. In the presence of CO, CO extracts an oxygen atom from Rh oxide clusters. The rate constants for oxygen extraction are higher for the more oxidized Rh clusters. Hence, it is expected that the catalytic activity of N2O reduction and CO oxidation by Rh clusters must be higher in oxidized states than in the completely metallic state. For the transition metal oxides such as Ni, they exhibits different reactivities to CO depending on the cluster size and stoichiometry; physisorption, chemisorption and CO oxidation. Though it was difficult, so far, to discriminate physisorption and chemisorption by the conventional mass spectrometry, we succeeded in discriminating them by using post heating method.