Adsorption, desorption, and reaction of methyl radicals on surface terminations of α-Fe2O3

Li Liu, Brian R. Quezada, Peter C Stair

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The adsorption, desorption, and reaction of gas phase methyl radicals were studied on the (0001)-oriented α-Fe2O3 surface in ultrahigh vacuum. Two different surface terminations were compared: An Fe 3O4 (111) layer and the so-called "biphase" surface thought to be a mixture of FeO and Fe2O3 terminations. Gas phase methyl radicals were prepared by pyrolysis of azomethane. On Fe3O4 (111) methyl radical adsorption forms surface methoxide species as determined by the C(1s) XPS binding energy. Temperature programmed reaction spectroscopy produced direct desorption of methyl radicals at all coverages and the formation of ethane at high coverages in two desorption peaks at 331 and 439 K. The activation energies for desorption were 84 and 133 kJ/mol in the two regimes. The two surface terminations exhibit saturation coverages that differ by ca., 30× : 1.5 × 10 14 and 5.2 × 1012 per cm2 for the Fe 3O4(111) and "biphase" terminations, respectively. These results are interpreted in terms of bonding models and differences in atomic structure for the two terminations.

Original languageEnglish
Pages (from-to)17105-17111
Number of pages7
JournalJournal of Physical Chemistry C
Volume114
Issue number40
DOIs
Publication statusPublished - Oct 14 2010

Fingerprint

Desorption
desorption
Adsorption
adsorption
Gases
vapor phases
Ethane
Ultrahigh vacuum
Binding energy
atomic structure
ethane
ultrahigh vacuum
pyrolysis
Pyrolysis
X ray photoelectron spectroscopy
Activation energy
binding energy
methyl radical
Spectroscopy
activation energy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Adsorption, desorption, and reaction of methyl radicals on surface terminations of α-Fe2O3. / Liu, Li; Quezada, Brian R.; Stair, Peter C.

In: Journal of Physical Chemistry C, Vol. 114, No. 40, 14.10.2010, p. 17105-17111.

Research output: Contribution to journalArticle

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AB - The adsorption, desorption, and reaction of gas phase methyl radicals were studied on the (0001)-oriented α-Fe2O3 surface in ultrahigh vacuum. Two different surface terminations were compared: An Fe 3O4 (111) layer and the so-called "biphase" surface thought to be a mixture of FeO and Fe2O3 terminations. Gas phase methyl radicals were prepared by pyrolysis of azomethane. On Fe3O4 (111) methyl radical adsorption forms surface methoxide species as determined by the C(1s) XPS binding energy. Temperature programmed reaction spectroscopy produced direct desorption of methyl radicals at all coverages and the formation of ethane at high coverages in two desorption peaks at 331 and 439 K. The activation energies for desorption were 84 and 133 kJ/mol in the two regimes. The two surface terminations exhibit saturation coverages that differ by ca., 30× : 1.5 × 10 14 and 5.2 × 1012 per cm2 for the Fe 3O4(111) and "biphase" terminations, respectively. These results are interpreted in terms of bonding models and differences in atomic structure for the two terminations.

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