Collision-induced dissociation and density functional theory studies of co adsorption over zirconium oxide cluster ions: Oxidative and nonoxidative adsorption

摘要

Zirconium oxide cluster cations and anions are produced by laser ablation and reacted with CO in a fast flow reactor. The CO adsorption products Zr _xO_yCO~+ are observed for most of the generated cationic clusters (Zr_xO_y~+ = Zr _2O_(5,6)~+, Zr_3O_(7,8)~+, Zr_4O_(9,10)~+?) while only specific anionic systems (Zr_xO_y~- = Zr _3O_7~-, Zr_4O_9~-?) absorb CO to produce Zr_xO_yCO ~-. To study how the CO molecule is adsorbed on the clusters, the Zr_xO_yCO~± products are mass-selected by a time-of-flight mass spectrometer (TOF-MS) and collided with a crossed helium beam. The fragment ions from collision-induced dissociation (CID) are detected by a secondary TOF-MS. Loss of CO and CO_2 is observed upon the collision of the helium beam with Zr_xO_yCO~+ and Zr_xO_(2x+1)CO~-, respectively. Density functional theory calculations indicate that oxidative and nonoxidative adsorption of CO takes place over Zr_3O_7~- and Zr _3O_7~+, respectively. This is consistent with the CID experiments.