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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
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Hydrogen migration dynamics in hydrated Al clusters: the Al17(-)·H2O system as an example
S Álvarez-Barcia1, J R Flores1
1Facultad de Química, Universidad de Vigo, E-36310-Vigo (Pontevedra), Spain.
The Journal of Chemical Physics
|March 5, 2014
Summary
Aluminum clusters interacting with water molecules can split water to produce hydrogen gas. Hydrogen atom migration on the cluster surface is key, but energy dissipation slows this process, limiting tunneling
Area of Science:
- Physical Chemistry
- Materials Science
- Computational Chemistry
Background:
- Aluminum clusters (Alm) interacting with water (H2O) can produce hydrogen gas (H2) via water splitting.
- Hydrogen atom migration on the cluster surface is crucial for the H2 production mechanism.
Purpose of the Study:
- Investigate the gas-phase evolution of HAl17(OH)((-)) as a model system for water splitting by aluminum clusters.
- Determine the role of hydrogen atom migration and tunneling in H2 generation.
Main Methods:
- Density Functional Theory (DFT) for locating energy minima and saddle points.
- Molecular Dynamics (MD) and Rice-Ramsperger-Kassel-Marcus (RRKM) theory with tunneling effects.
Main Results:
- The H atom, after bonding to the Al cluster in Al17((-))·(H2O) → HAl17(OH)((-)), rapidly loses excess energy due to cluster flexibility.
- This rapid energy dissipation significantly slows down long-range hydrogen migration.
- Tunneling effects appear to play a secondary role in migration dynamics at moderate energies.
Conclusions:
- The flexibility of aluminum clusters facilitates rapid energy absorption, hindering efficient hydrogen atom migration.
- The study suggests that hydrogen migration, not tunneling, is the rate-limiting step in H2 production for this model system.
- Understanding these dynamics is crucial for designing efficient hydrogen generation processes using aluminum clusters and water.
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