CO oxidation by neutral gold-vanadium oxide clusters

Abstract

Oxidation of CO by gas-phase atomic clusters is being actively studied to understand the molecular-level mechanisms of heterogeneous CO oxidation over related catalytic surfaces. However, it is experimentally challenging to study CO oxidation by neutral heteronuclear metal oxide clusters because of the difficulty of cluster ionization and detection without fragmentation. Herein, the neutral AuVO 2−4 clusters were experimentally generated and their reactions with CO and O 2 were studied. The experimental results showed that CO adsorption is the dominant channel on the interactions of AuVO 4 and AuVO 3 with CO, and AuVO 2 can pick up an O 2 molecule to generate AuVO 4 . Theoretical studies indicated that the oxidation of the trapped CO in AuVO 3,4 CO into CO 2 is exothermic while the reaction barriers have to be overcome at the elevated temperatures. A catalytic cycle for CO oxidation by AuVO 2−4 is proposed.

Catalytic CO Oxidation by O2 Mediated with Single Gold Atom Doped Titanium Oxide Cluster Anions AuTi2O4–6−

“…[26] Thus, related fundamental studies are of scientific and practical importance to provide suggestive information to tailor the active sites. In gas-phase studies, for catalytic CO oxidation by O 2 mediated with gold-containing HMOCs, [16,17,22] gold was reinforced to function as a powerful electron reservoir to promote CO oxidation and O 2 activation. Herein, the catalysis driven by the AuTi 2 O 4-6 À cluster anions provides new insights into the importance of the Ti 2 O 4 moiety in O 2 activation.…”

“…This behavior is in sharp contrast to our previous results that the O 2 À • species cannot be ruptured directly and an intermediate with an O 2 2À unit always exist along the pathway. [16][17][18][19]22] Herein, the electrons (0.88 e) required for the complete dissociation of the O 2 À • unit ( 3 I16!AuTi 2 O 6 À ) come from both of the Au atom (0.58 e, + 0.12 e in 3 I16 versus 0.71 e in AuTi 2 O 6 À ) and the Ti 2 O 4 moiety (0.30 e, À 0.78 e in 3 I16 versus À 0.48 e in AuTi 2 O 6 À ), as shown in Figure 5, emphasizing the crucial roles of the Ti 2 O 4 moiety to act as a transfer station for electrons. This phenomenon also indicates that the AuTi 2 O 4 À cluster anion can eject enough electrons to drive the direct It has been evidenced that the charge state of clusters can exhibit a significant effect on their reactivity and mechanisms.…”

“…Gold catalysis is a fascinating topic in both of the gas-phase and condensedphase studies since the breakthrough made by Haruta and coworkers that Au/TiO 2 with supported nanosized gold catalysts exhibited extraordinary activity for catalytic CO oxidation at low temperatures. [12,13] CO oxidation is also one type of the best studied catalytic reactions in gas phase, [1,14,15] and gold-contain-ing heteronuclear metal oxide clusters (HMOCs) [16][17][18][19][20][21][22][23][24] are promising models for the active sites on oxide supported gold. Catalytic CO oxidation by O 2 mediated with Au-TiÀ O HMOCs is of great importance to uncover the catalytic behaviors of Au/ TiO 2 , one type of the best studied gold catalysts in condensedphase studies until now.…”

“…[17] However, catalytic CO oxidation by O 2 mediated with Au-TiÀ O cluster ions has not been identified. The activation and dissociation of molecular O 2 over gold catalysts is generally regarded as the pivotal steps in both of the gas phase [16][17][18][19]23] and condensed phase studies, [31,32] and the species with closed-shell electronic structure are generally inert or much less reactive toward O 2 . [33][34][35] [17] Recently, we reported the scarce examples that the CuAl 4 O 7 À [36] and the AuVO 2 [16] clusters with closed-shell electronic structure can activate O 2 into superoxide (O 2 À •) and peroxide (O 2 2À ) species, respectively.…”

“…The activation and dissociation of molecular O 2 over gold catalysts is generally regarded as the pivotal steps in both of the gas phase [16][17][18][19]23] and condensed phase studies, [31,32] and the species with closed-shell electronic structure are generally inert or much less reactive toward O 2 . [33][34][35] [17] Recently, we reported the scarce examples that the CuAl 4 O 7 À [36] and the AuVO 2 [16] clusters with closed-shell electronic structure can activate O 2 into superoxide (O 2 À •) and peroxide (O 2 2À ) species, respectively. In this study, by using mass spectrometry and quantum chemical calculations, we demonstrate unambiguously that the single gold atom doped titanium oxide cluster anion AuTi 2 O 4 À with closed-shell electronic structure can effectively activate O 2 molecule into atomic oxygen in product AuTi 2 O 6 À , which can oxidize two CO molecules consecutively [23] and then a cycle of CO oxidation catalyzed by the AuTi 2 O 4-6…”