Both ceria (CeO2)and alumina (Al2O3) are very important catalyst supportmaterials. Neutral binary oxide nanoclusters (NBONCs), CexAlyOz, are generated and detectedin the gas phase and their reactivity with carbon monoxide (CO) and butane (C4H10)is studied. The very active species CeAlO4� can react with CO and butane via O atom transfer (OAT) and H atomtransfer (HAT), respectively. Other CexAlyOz NBONCs do not showreactivities toward CO and C4H10. The structures, as well as the reactivities, of CexAlyOzNBONCs are studiedtheoretically employing density functional theory (DFT) calculations. The ground state CeAlO4� NBONC possesses a kite-shaped structure with an OtCeObObAlOtconfiguration (Ot, terminal oxygen; Ob, bridging oxygen).An unpaired electron is located on the Ot atom of the AlOtmoiety rather than the CeOt moiety: this Ot centeredradical moiety plays a very important role for the reactivity of the CeAlO4� NBONC. The reactivities of Ce2O4,CeAlO4, and Al2O4 toward CO are compared,emphasizing the importance of a spin-located terminal oxygen for thesereactions. Intramolecular charge distributions do not appear to play a role inthe reactivities of these neutral clusters, but could be important for chargedisoelectronic BONCs. DFT studies show that the reaction of CeAlO4� with C4H10 to form the CeAlO4H�C4H9� encounter complex is barrierless. While HAT processes have beenpreviously characterized for cationic and anionic oxide clusters, the reportedstudy is the first observation of a HAT process supported by a ground stateneutral oxide cluster. Mechanisms for catalytic oxidation of CO over surfacesof AlxOy/MmOn or MmOn/AlxOymaterials are proposed consistent with the presented experimental andtheoretical results.

Gas phase Ce/Al neutral binary oxide clusters: Distribution, structure, and reactivity

247th National Meeting (2014)

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