Hydrogen migration dynamics in hydrated Al clusters: The Al{sub 17}{sup (−)}·H{sub 2}O system as an example
The Al{sub m}{sup (−)}·(H{sub 2}O){sub n} systems are known to undergo water splitting processes in the gas phase giving H{sub k}Al{sub m}(OH){sub k}{sup (−)}·(H{sub 2}O){sub n−k} systems, which can generate H{sub 2}. 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 H{sub 2} 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 HAl{sub 17}(OH){sup (−)}, 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 Al{sub 17}{sup (−)}·(H{sub 2}O) → HAl{sub 17}(OH){sup (−)}, 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 H{sub 2} generation from the interaction of Al clusters and water molecules are discussed.
- OSTI ID:
- 22255054
- Journal Information:
- Journal of Chemical Physics, Vol. 140, Issue 8; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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