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

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⁺, Zr₃O_7,8 ⁺, Zr₄O_9,10⁺⋯) while only specific anionic systems (Zr_xO_y^- = Zr ₃O₇^-, Zr₄O₉ ^-⋯) 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 CO₂ is observed upon the collision of the helium beam with Zr_xO_yCO⁺ and Zr_xO_2x+1CO^-, respectively. Density functional theory calculations indicate that oxidative and nonoxidative adsorption of CO takes place over Zr₃O₇^- and Zr ₃O₇⁺, respectively. This is consistent with the CID experiments.