RESUMEN
Cerium oxide cationic clusters (CeO2)1-3(+) were generated through laser ablation and then reacted with sulfur dioxide (SO2) at ambient conditions in an ion trap reactor and those reactions were studied and characterized by combining the art of time-of-flight mass spectrometry (TOF-MS) with density functional theory (DFT) calculations. Molecule association and oxygen atom transfer (OAT) were observed for the CeO2(+) and (CeO2)2,3(+) reaction systems, respectively. The mechanistic analysis indicates that the weak Ce-O bond strength associated with the oxygen release capacity of cerium oxide clusters is considered as the key factor to achieve the oxidation of SO2. To our best knowledge, this research should be the first example to identify the OAT reactivity of metal oxide cluster ions toward sulfur dioxide under thermal collision conditions, and a fundamental understanding of the elementary oxidation of SO2 to SO3 is provided.
RESUMEN
In addition to generation of a methyl radical, formation of a formaldehyde molecule was observed in the thermal reaction of methane with AuNbO3(+) heteronuclear oxide cluster cations. The clusters were prepared by laser ablation and mass-selected to react with CH4 in an ion-trap reactor under thermal collision conditions. The reaction was studied by mass spectrometry and DFT calculations. The latter indicated that the gold atom promotes formaldehyde formation through transformation of an Au-O bond into an Au-Nb bond during the reaction.
RESUMEN
A molecular-level insight into the nature of reactive oxygen species involved in dihydrogen (H2 ) dissociation is of great importance to understand gold catalysis. In this study, laser ablation generated and mass-selected AuNbO4+ oxide cluster cations could dissociate H2 in an ion-trap reactor. The reaction has been characterized by time-of-flight mass spectrometric experiments and density functional calculations. The lowest energy isomer of AuNbO4+ contains two lattice oxygen (O2- ) and one superoxide (O2.- ) species. The gold atom anchors the H2 molecule in the first step and then delivers one hydrogen atom to the O2- ion in H2 dissociation. At the same time, O2.- is reduced into a peroxide unit that can accept the second hydrogen atom of H2 with the generation of a hydroxyl radical as the main product. In this study, the important roles of the O2.- unit in the dissociation of H2 have been identified.