jp2098153_si_001.pdf (1.04 MB)
Atomic Oxygen on Graphite: Chemical Characterization and Thermal Reduction
journal contribution
posted on 2012-05-10, 00:00 authored by Rosanna Larciprete, Paolo Lacovig, Sandra Gardonio, Alessandro Baraldi, Silvano LizzitThe chemisorption of O atoms on graphite and the thermal
reduction
of the oxidized surface were studied by means of high energy resolution
photoelectron spectroscopy with synchrotron radiation. The C 1s and
O 1s core levels and the valence band spectra were used to identify
the different oxidizing surface species and to evaluate the extension
of the sp2 conjugation as a function of oxidation time
and annealing temperature. We found that epoxy groups are the dominant
species only at the low oxidation stage, and ethers and semiquinones
form as oxidation proceeds. The evolution of the ether/epoxy ratio
with increasing oxygen coverage provides evidence for the occurrence
of C–C bond unzipping. Epoxy groups are the functionalities
with the lowest thermal stability and start to desorb around 370 K,
strongly affecting the desorption temperature of other functional
groups. The ratio between ethers and epoxy groups determines the balance
between epoxy–epoxy and epoxy–ether reactions, the latter
promoting the removal of C atoms from the C backbone. Adsorbate spectroscopy
during thermal annealing definitely proves the catalytic effect of
the basal plane oxygen atoms on the desorption reactions.
History
Usage metrics
Categories
Keywords
basal plane oxygen atomsoxidation timeoxidizing surface speciessynchrotron radiationAdsorbate spectroscopyThermal ReductionThe chemisorption370 Kcore levelsenergy resolution photoelectron spectroscopyratioEpoxy groupsChemical Characterizationethersp 2 conjugationvalence band spectrasemiquinones formoxidation proceedsC backboneO 1O atomsC 1desorption temperatureannealing temperatureAtomic Oxygendesorption reactionsoxygen coverageoxidation stageC atoms