A New Surface Oxygen Complex on Carbon: Toward a Unified Mechanism for Carbon Gasification Reactions

Molecular orbital theory calculations and recent high-temperature TPD experiments revealed the feasibility of a new type of active oxygen complex on graphite. This type of complex is formed by bonding of an oxygen atom to a saturated carbon atom (in the caved-in position) adjacent to the unsaturated edge carbon atom that is already bonded to an oxygen atom. Molecular orbital calculation results also show that this type of complex is substantially more active than the known complexes that have been discussed in the literature, e.g., semiquinones and carbonyls. On the basis of this new type of complex, a unified mechanism is proposed for the gasification reactions of carbon with all oxygen-containing gases. The proposed mechanism can account for all major features of the published experimental results on temperature-programmed desorption, transient kinetic, and steady-state rate studies of the gas-carbon reactions.