Surface Chemistry of Transition Metal Carbides: A Theoretical Analysis.
Abstract
Extended Huckel tight binding calculations have been employed to analyze the interactions of oxygen, carbon monoxide and methanol with the (100) and (111) faces of a representative rocksalt carbide, TiC. The (111) face have been experimentally shown to be the most active toward the adsorption, dissociation or decomposition of adsorbates, whereas the (100) face demonstrates very little activity. Calculations suggest that the differential reactivity of the two faces is the result of the coordination of the atom in the active site and the presence of surface carbon. For CO on the (100) the population of the 2Pi* level increases if carbon vacancies are included in the calculations and dissociated occurs. For the (111) metal-terminated face of TiC the population of the 2Pi* level is nearly identical to that calculated for Ti(0001). Methanol dissociates into methoxy and a protic species on the (111) face but remains molecular on the (100). The calculations suggest that the molecular species is stabilized by interaction of the methanolic proton with the surface carbon.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1987
- Accession Number
- ADA184237
Entities
People
- Roald Hoffmann
- Susan A. Jansen
Organizations
- Cornell Laboratory of Atomic and Solid State Physics