Complementary Active Sites Cause Size-Selective Reactivity of Aluminum Cluster Anions with Water

Roach, Patrick J.; Woodward, W. Hunter; Castleman, A. W.; Reber, Arthur C.; Khanna, Shiv N.

doi:10.1126/science.1165884

Cited by 272 publications

(315 citation statements)

References 22 publications

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“…Clusters of this kind composed of tungsten and oxygen are reported for the first time in the gas phase. The presence of prominent peaks for W 6 -, especially for these compositions is supported by the computed atomization energies of these clusters which reveal enhanced stabilities for these compositions. Structure and stability of these unique magic numbered clusters will be of great interest, especially for their catalytic applications.…”

Section: Resultsmentioning

confidence: 63%

“…Closed-cage clusters of composition, W 6 -were detected in the laser desorption mass spectra of W-Se and W-S mixtures. Further study of the precursor revealed the formation of nano tungsten oxide from a mixture of W and Se.…”

Section: Resultsmentioning

confidence: 98%

“…Structure and reactivity of specific Al clusters such as Al 12 , Al 16 , Al 17 , and Al 18 have been extensively explored by Castleman and Khanna. 6 Magic-numbered silver clusters formed by matrix-assisted laser desorption mass spectrometry were reported by Kéki et al 7 Apart from monometallic clusters, they also reported bimetallic Ag-Au clusters. 8 Many kinds of transition metal oxide clusters have been explored in the gas phase.…”

Section: Introductionmentioning

confidence: 92%

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Closed-Cage Tungsten Oxide Clusters in the Gas Phase

et al. 2010

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During the course of a study on the clustering of W-Se and W-S mixtures in the gas phase using laser desorption ionization (LDI) , stand out as intense peaks in the regular mass spectral pattern of tungsten oxide clusters suggesting unusual stabilities for them. Moreover, these clusters do not fragment in the postsource decay analysis. While trying to understand the precursor material, which produced these clusters, we found the presence of nanoscale forms of tungsten oxide. The structure and thermodynamic parameters of tungsten clusters have been explored using relativistic quantum chemical methods. Our computed results of atomization energy are consistent with the observed LDI mass spectra. The computational results suggest that the clusters observed have closed-cage structure. These distinct W 13 and W 14 clusters were observed for the first time in the gas phase.

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Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 92%

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Closed-Cage Tungsten Oxide Clusters in the Gas Phase

et al. 2010

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“…Conventional ab initio molecular dynamics simulation has revealed rapid hydrogen production from water by a cluster (or superatom) consisting of a magic number of aluminum atoms, Al 17 . We found a low activation-barrier mechanism, in which a pair of Lewis acid and base sites on the Al n surface preferentially catalyzes hydrogen production.…”

Section: Discussionmentioning

confidence: 99%

“…This is followed by a chain of hydrogen bond switching events (denoted by arrows in figure 9(a)) that involves in total of four H 2 O molecules, and finally a hydrogen atom bonds to an Al atom after 190 fs. This proton transfer is induced by the Lewis acidbase characters of the participating Al atoms [17]. Although it is hard for the water molecule to dissociate by itself, the Grotthuss mechanism greatly reduces the activation barrier for the dissociation.…”

Section: Low Activation-barrier Mechanism Of Hydrogen Productionmentioning

confidence: 99%

Large-scale atomistic simulations of nanostructured materials based on divide-and-conquer density functional theory

Shimojo

Ohmura

Nakano

et al. 2011

EPJ Web of Conferences

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Abstract.A linear-scaling algorithm based on a divide-and-conquer (DC) scheme is designed to perform large-scale molecular-dynamics simulations, in which interatomic forces are computed quantum mechanically in the framework of the density functional theory (DFT). This scheme is applied to the thermite reaction at an Al/Fe 2 O 3 interface. It is found that mass diffusion and reaction rate at the interface are enhanced by a concerted metal-oxygen flip mechanism. Preliminary simulations are carried out for an aluminum particle in water based on the conventional DFT, as a target system for large-scale DC-DFT simulations. A pair of Lewis acid and base sites on the aluminum surface preferentially catalyzes hydrogen production in a low activation-barrier mechanism found in the simulations.

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Evidence of a Kinetic Isotope Effect in Nanoaluminum and Water Combustion

2014

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The normally innocuous combination of aluminum and water becomes violently reactive on the nanoscale. Research in the field of the combustion of nanoparticulate aluminum has important implications in the design of molecular aluminum clusters, hydrogen storage systems, as well as energetic formulations which could use extraterrestrial water for space propulsion. However, the mechanism that controls the reaction speed is poorly understood. While current models for micron‐sized aluminum water combustion reactions place heavy emphasis on diffusional limitations, as reaction scales become commensurate with diffusion lengths (approaching the nanoscale) reaction rates have long been suspected to depend on chemical kinetics, but have never been definitely measured. The combustion analysis of nanoparticulate aluminum with H2O or D2O is presented. Different reaction rates resulting from the kinetic isotope effect are observed. The current study presents the first‐ever observed kinetic isotope effect in a metal combustion reaction and verifies that chemical reaction kinetics play a major role in determining the global burning rate.

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Complementary Active Sites Cause Size-Selective Reactivity of Aluminum Cluster Anions with Water

Cited by 272 publications

References 22 publications

Closed-Cage Tungsten Oxide Clusters in the Gas Phase

Closed-Cage Tungsten Oxide Clusters in the Gas Phase

Large-scale atomistic simulations of nanostructured materials based on divide-and-conquer density functional theory

Evidence of a Kinetic Isotope Effect in Nanoaluminum and Water Combustion

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