Grant Johnson - Effect of charge state and stoichiometry on the structure and reactivity of nickel oxide clusters with CO

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  Publication Details (including relevant citation   information):


  Volume:   280

    Issue: 1-3

    Pages: 93-100


Published: FEB 1 2009


    The collision induced fragmentation and reactivity of cationic   and anionic nickel oxide clusters with carbon monoxide were   studied experimentally using guided-ion-beam mass spectrometry.   Anionic clusters with a stoichiometry containing one more oxygen   atom than nickel atom (NiO(2), Ni(2)O(3), Ni(3)O(4) and   Ni(4)O(5)) were found to exhibit dominant products resulting from   the transfer of a single oxygen atom to CO, suggesting the   formation of CO(2). Of these four species, Ni(2)O(3) and   Ni(4)O(5) were observed to be the most reactive having oxygen   transfer products accounting for approximately 5% and 10% of the   total ion intensity at a maximum pressure of 15 mTorr of CO. Our   findings, therefore, indicate that anionic nickel oxide Clusters   containing an even number of nickel atoms and an odd number of   oxygen atoms are more reactive than those with an odd number of   nickel atoms and an even number of oxygen atoms. The majority of   cationic nickel oxides, in contrast to anionic species, reacted   preferentially through the adsorption of CO, onto the Cluster   accompanied by the loss of either molecular O(2) or nickel oxide   units. The adsorption of CO onto positively charged nickel   oxides, therefore, is exothermic enough to break apart the   gas-phase clusters. Collision induced dissociation experiments,   employing inert xenon gas, were also conducted to gain insight   into the structural properties of nickel oxide clusters. The   fragmentation products were found to vary considerably with size   and stoichiometry as well as ionic charge state. In general,   cationic clusters favored the collisional loss of molecular O(2)   while anionic clusters fragmented through the loss of both atomic   oxygen and nickel oxide units. Our results provide insight into   the effect of ionic charge state on the structure of nickel oxide   clusters. Furthermore, we establish how the size and   stoichiometry of nickel oxide Clusters influences their ability   to oxidize CO, an important reaction for environmental pollution   abatement.

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