Active sites in graphene and the mechanism of CO2 formation in carbon oxidation

Research output: Contribution to journalArticle

126 Citations (Scopus)

Abstract

Over the past decade we have witnessed a steady rise in contributions of computational quantum chemistry to the understanding of reactivity of carbon materials. Several litmus tests must be applied to this evolving body of work before it can be viewed with a sufficient degree of confidence. The results of a crucial test are presented here: formulation of thermodynamically and kinetically plausible paths for CO2 formation in the deceivingly simple reaction C + (1 - y/2)O2 = (1 - y)CO2 + yCO. A mechanism is proposed that clarifies the nature of atoms responsible for adsorption and reaction of molecular oxygen on the surface of sp 2-hybridized carbons, both flat and curved, and is also consistent with the postulate that the (re)active sites are carbene- and carbyne-type carbon atoms at graphene edges. Using density functional theory and representative two-dimensional graphene clusters, a direct and an indirect route to CO2 formation were identified as both necessary and sufficient to account for key experimental observations. The former involves single-site O2 adsorption on carbene-type zigzag edges. The latter includes the presence of mobile epoxide-type oxygen on the basal plane and its insertion into an edge hexagon, analogous to the conversion of benzene oxide to oxepin; such "unzipping" of graphene and CO2 desorption is favored at oxygen-saturated edges, thus accounting for the well-documented phenomenon of induced heterogeneity of carbon reactive sites.

Original languageEnglish (US)
Pages (from-to)17166-17175
Number of pages10
JournalJournal of the American Chemical Society
Volume131
Issue number47
DOIs
StatePublished - Dec 2 2009

Fingerprint

Graphite
Graphene
Catalytic Domain
Carbon
Oxidation
Oxygen
Adsorption
Oxepins
Computational chemistry
Quantum chemistry
Atoms
Molecular oxygen
Epoxy Compounds
Density functional theory
Desorption
Benzene
Oxides
carbene

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

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abstract = "Over the past decade we have witnessed a steady rise in contributions of computational quantum chemistry to the understanding of reactivity of carbon materials. Several litmus tests must be applied to this evolving body of work before it can be viewed with a sufficient degree of confidence. The results of a crucial test are presented here: formulation of thermodynamically and kinetically plausible paths for CO2 formation in the deceivingly simple reaction C + (1 - y/2)O2 = (1 - y)CO2 + yCO. A mechanism is proposed that clarifies the nature of atoms responsible for adsorption and reaction of molecular oxygen on the surface of sp 2-hybridized carbons, both flat and curved, and is also consistent with the postulate that the (re)active sites are carbene- and carbyne-type carbon atoms at graphene edges. Using density functional theory and representative two-dimensional graphene clusters, a direct and an indirect route to CO2 formation were identified as both necessary and sufficient to account for key experimental observations. The former involves single-site O2 adsorption on carbene-type zigzag edges. The latter includes the presence of mobile epoxide-type oxygen on the basal plane and its insertion into an edge hexagon, analogous to the conversion of benzene oxide to oxepin; such {"}unzipping{"} of graphene and CO2 desorption is favored at oxygen-saturated edges, thus accounting for the well-documented phenomenon of induced heterogeneity of carbon reactive sites.",
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Active sites in graphene and the mechanism of CO2 formation in carbon oxidation. / Radovic, Ljubisa R.

In: Journal of the American Chemical Society, Vol. 131, No. 47, 02.12.2009, p. 17166-17175.

Research output: Contribution to journalArticle

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