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- Title
DFT and kinetics study of O/O mixtures reacting over a graphite (0001) basal surface.
- Authors
Morón, Víctor; Gamallo, Pablo; Sayós, Ramón
- Abstract
Spin-polarized density functional calculations were used to investigate the interaction of atomic and molecular oxygen on the basal graphite surface at several atomic coverages. Two carbon layers were enough to represent the graphite surface. Oxygen atoms bind mainly over C-C bridge sites forming an epoxide-like structure with a two carbon puckering and with adsorption energies in the 0.95-1.28 eV range, depending on the atomic coverage. Molecular oxygen only shows a very weak physisorption. Atomic adsorption and diffusion along with atomic recombination via Eley-Rideal and Langmuir-Hinshelwood mechanisms were studied. All surfaces processes were activated with energy barriers that decreased for lower atomic coverages. Relaxation effects were non-negligible. A microkinetic model with six elementary surface processes was proposed to see the overall behaviour of several initial O/O mixtures flowing over a graphite surface at 300-1,000 K. Thermal rate constants were derived from Density Functional Theory data and standard Transition State Theory. A very low steady-state atomic coverage (θ < 0.5%) was predicted, and also very low atomic recombination coefficients were observed (γ < 5 × 10). The Eley-Rideal together with the adsorption and desorption processes was much more important than the Langmuir-Hinshelwood reaction.
- Subjects
ADSORPTION (Chemistry); DIFFUSION; GRAPHITE; DENSITY functionals; CHEMICAL kinetics; SURFACES (Technology); ATOMIC theory; RELAXATION phenomena
- Publication
Theoretical Chemistry Accounts: Theory, Computation, & Modeling, 2011, Vol 128, Issue 4-6, p683
- ISSN
1432-881X
- Publication type
Article
- DOI
10.1007/s00214-010-0798-3