Reactions of NO, O 2, H 2O, and CO 2 with the basal plane of graphite

Abstract

The reactions of NO, O 2, H 2O, and CO 2 with graphite between 400 and 900°C have been studied by STM to obtain quantitative kinetics by measuring the number and size of monolayer pits on the basal plane versus temperature and time. At low temperature, reactions initiate exclusively from point defect sites on the basal plane of graphite, forming circular or hexagonal pits one monolayer deep of uniform radius which varies linearly with time and can be used to obtain quantitative kinetics. The activation energies of the monolayer reactions on graphite vary from 89 kJ/mol with NO to 205 kJ/mol with H 2O. At higher temperature, these gases also react with carbon atoms in the basal plane, creating new defect sites which nucleate monolayer pit formation. This was examined quantitatively by counting the number of pits versus time and temperature. Activation energies of basal plane attack vary from 164 kJ/mol with NO to 370 kJ/mol with H 2O.