Reaction of aluminum clusters with water

Ohmura, Satoshi; Shimojo, Fuyuki; Kalia, Rajiv K.; Kunaseth, Manaschai; Nakano, Aiichiro; Vashishta, Priya

doi:10.1063/1.3602326

Cited by 43 publications

(48 citation statements)

References 51 publications

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“…[40][41][42][43][44][45][46] It includes also a number of theoretical studies on the structural aspects of Al clusters, [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] and about their interaction [65][66][67][68][69][70][71][72] and reaction [73][74][75][76][77][78][79] with simple molecules.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen migration dynamics in hydrated Al clusters: The Al17(−)·H2O system as an example

Álvarez‐Barcia¹,

Flores²

2014

The Journal of Chemical Physics

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The Alm((-))·(H2O)n systems are known to undergo water splitting processes in the gas phase giving HkAlm(OH)k((-))·(H2O)n-k systems, which can generate H2. The migration of H atoms from one Al atom to another on the cluster's surface is of critical importance to the mechanism of the complete H2 production process. We have applied a combination of Molecular Dynamics and Rice-Ramsperger-Kassel-Marcus theory including tunneling effects to study the gas-phase evolution of HAl17(OH)((-)), which can be considered a model system. First, we have performed an extensive search for local minima and the connecting saddle points using a density functional theory method. It is found that in the water-splitting process Al17((-))·(H2O) → HAl17(OH)((-)), the H atom which bonds to the Al cluster losses rather quickly its excess energy, which is easily "absorbed" by the cluster because of its flexibility. This fact ultimately determines that long-range hydrogen migration is not a very fast process and that, probably, tunneling only plays a secondary role in the migration dynamics, at least for moderate energies. Reduction of the total energy results in the process being very much slowed down. The consequences on the possible mechanisms of H2 generation from the interaction of Al clusters and water molecules are discussed.

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Section: Introductionmentioning

confidence: 99%

Hydrogen migration dynamics in hydrated Al clusters: The Al17(−)·H2O system as an example

Álvarez‐Barcia¹,

Flores²

2014

The Journal of Chemical Physics

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“…20,21 The observed fast reaction rates and calculated low reaction energy barriers are explained by the same reaction mechanisms as in our previous study. 22,23 In addition, we find that the formation and breaking up of branching H-bonds, which connect the H-bond chain with the solvation shell, are crucial to facilitate proton transfer. This explains why the energy barrier varies strongly upon the rearrangement of surrounding water molecules, generally resulting in extremely low values (< 0.1 eV) in the presence of branching H-bonds.…”

Section: Introductionmentioning

confidence: 99%

“…Our previous quantum molecular dynamics (MD) study investigated H 2 production of the magic-number Al n (n = 12, 17) in liquid water. 22,23 It is found that proton transfer along a chain of hydrogen bonds (H-bonds) between water molecules, i.e. Grotthuss mechanism, [24][25][26][27][28] plays an important role not only in splitting water into surface hydrogen and hydroxyl groups, but also in recombining hydrogen atoms into hydrogen molecules.…”

Section: Introductionmentioning

confidence: 99%

Effects of solvation shells and cluster size on the reaction of aluminum clusters with water

et al. 2011

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Reaction of aluminum clusters, Aln (n = 16, 17 and 18), with liquid water is investigated using quantum molecular dynamics simulations, which show rapid production of hydrogen molecules assisted by proton transfer along a chain of hydrogen bonds (H-bonds) between water molecules, i.e. Grotthuss mechanism. The simulation results provide answers to two unsolved questions: (1) What is the role of a solvation shell formed by non-reacting H-bonds surrounding the H-bond chain; and (2) whether the high size-selectivity observed in gas-phase Aln-water reaction persists in liquid phase? First, the solvation shell is found to play a crucial role in facilitating proton transfer and hence H2 production. Namely, it greatly modifies the energy barrier, generally to much lower values (< 0.1 eV). Second, we find that H2 production by Aln in liquid water does not depend strongly on the cluster size, in contrast to the existence of magic numbers in gas-phase reaction. This paper elucidates atomistic mechanisms underlying these observations

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“…12 Other ligand-stabilized metal clusters are known in addition to the aluminum compounds; thiolprotected gold clusters, for example, have received significant recent attention due to their application in nanomedicine and biochemistry. 8,9,20 Beyond the basic interest in ligand-protected cluster stability, there is also recent interest in the use of small aluminum clusters as catalysts for producing hydrogen from water 21,22 or as high energy-density fuels. 23 Aluminum powder is frequently used as a fuel component due to its high enthalpy of combustion.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of ligand-protected aluminum clusters: An ab initio molecular dynamics study

Alnemrat

Hooper

2014

The Journal of Chemical Physics

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Oxidation of ligand-protected aluminum clusters: an ab-initio molecular dynamics study. "J. Chem. Phys. 140, 104313 (2014 We report Car-Parrinello molecular dynamics simulations of the oxidation of ligand-protected aluminum clusters that form a prototypical cluster-assembled material. These clusters contain a small aluminum core surrounded by a monolayer of organic ligand. The aromatic cyclopentadienyl ligands form a strong bond with surface Al atoms, giving rise to an organometallic cluster that crystallizes into a low-symmetry solid and is briefly stable in air before oxidizing. Our calculations of isolated aluminum/cyclopentadienyl clusters reacting with oxygen show minimal reaction between the ligand and O 2 molecules at simulation temperatures of 500 and 1000 K. In all cases, the reaction pathway involves O 2 diffusing through the ligand barrier, splitting into atomic oxygen upon contact with the aluminum, and forming an oxide cluster with aluminum/ligand bonds still largely intact. Loss of individual aluminum-ligand units, as expected from unimolecular decomposition calculations, is not observed except following significant oxidation. These calculations highlight the role of the ligand in providing a steric barrier against oxidizers and in maintaining the large aluminum surface area of the solid-state cluster material. [http://dx

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Reaction of aluminum clusters with water

Cited by 43 publications

References 51 publications

Hydrogen migration dynamics in hydrated Al clusters: The Al17(−)·H2O system as an example

Hydrogen migration dynamics in hydrated Al clusters: The Al17(−)·H2O system as an example

Effects of solvation shells and cluster size on the reaction of aluminum clusters with water

Oxidation of ligand-protected aluminum clusters: An ab initio molecular dynamics study

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