Vacuum Ultraviolet Ionization-Induced Reaction of Neutral Au₂Al₂O₃ Clusters with Methane

Abstract

Identification of molecular-level mechanisms of methane activation is very important in order to transform the most stable alkane molecule into valueadded chemicals. Herein, by employing a homemade time-of-flight mass spectrometer coupled with a vacuum ultraviolet (VUV) laser system, the reactions of neutral heteronuclear metal oxide clusters Au x Al y O z (x = 1, 2) with CH 4 have been investigated. The interesting channel of Au 2 Al 2 O 3 H + production was observed for the interaction of a Au 2 Al 2 O 3 cluster with CH 4 after VUV ionization, suggesting that the methyl radical was generated. Combined with the theoretical calculations, this study proposes that VUV ionization of the neutral adsorption complex (Au 2 Al 2 O 3 CH 4 ) creates an active cation (Au 2 Al 2 O 3 CH 4 + )* to induce C−H bond activation and the methyl radical formation. The photochemistry of this cluster study provides molecular-level insights into the interactions between methane and active sites in related photocatalytic processes.

Enhanced Catalysis of Pt 3 Clusters Supported on Graphene for N–H Bond Dissociation

“…[23][24][25][26][27] By conducting investigations of metal cluster catalysis, extensive efforts have been made to improve the reaction activity, and it is recognized that the specific sizes and geometric/electronic structures of clusters are often crucial factors in determining the resulting mechanisms and reaction rates. [28][29][30][31][32][33] Also, the binding energies can fluctuate with increasing numbers of atoms, allowing clusters at a certain size to transform from a two-dimensional planar structure to a three-dimensional (3-D) structure (e.g., Pt 3 vs Pt 4 ), and occasionally leading to "magic" number species such as Al 13 − , Ag 13 − , and 12,[34][35][36] In many studies, clusters are supported on a selected substrate in order to evaluate the catalytic reactions in a practical way. The interaction between the metal clusters and support is a fundamental characteristic in heterogeneous catalysis and plays an essential role in elucidating the electronic structures, adsorption behavior, and catalytic activities.…”

Oxidation of Isoprene by Neutral Iron Oxide Nanoclusters in the Gas Phase

“…A previous study indicated that in some rare cases the VUV ionization can lead to chemical reaction in the ionic state (Au 2 Al 2 O 3 + CH 4 → Au 2 Al 2 O 3 CH 4 , Au 2 Al 2 O 3 CH 4 + hv 118 nm → Au 2 Al 2 O 3 CH 4 + + e – , Au 2 Al 2 O 3 CH 4 + → Au 2 Al 2 O 3 H + + CH 3 ) . The generation of products such as CH 2 O (and Fe x O y –1 C 4 H 6 + ) may also be due to the VUV ionization.…”

“…As a result, it is important to use the computational method to support the experimental observation/suggestion (reactions 2−4). Because it is very rare to observe the reaction upon single-photon VUV ionization, 70 we consider that the reactivity for most of the clusters in this study is due to the neutral state reaction.…”

“…A previous study indicated that in some rare cases the VUV ionization can lead to chemical reaction in the ionic state 70 The generation of products such as CH 2 O (and Fe x O y−1 C 4 H 6 + ) may also be due to the VUV ionization. As a result, it is important to use the computational method to support the experimental observation/suggestion (reactions 2−4).…”

CO oxidation by neutral gold-vanadium oxide clusters

“…Benefiting from this experimental instrument, the size-dependent reactivity of nanosized neutral manganese oxide clusters Mn 2N O 3N +x (N =2−22; x=−1, 0, 1) toward ethylene was studied [25]. Moreover, on the reaction of Au 2 Al 2 O 3 with methane, the elimination of methyl radical was observed after VUV ionization [26].…”