(638h) Reaction of Methylene On α-Fe2O3(10-12)

Methylene, :CH₂, has been produced via the thermal dissociation of CH₂I₂ to examine the reaction of this simple carbene on α-Fe₂O₃(10-12). Thermal desorption experiments indicate the existence of multiple reaction pathways for surface methylene depending on the stoichiometry of the surface. The reaction of methylene on the nearly-stoichiometric surface produces CO₂ and CO as the primary carbon-containing products, formed via the consumption of surface lattice oxygen. As the surface becomes reduced, formaldehyde, H₂CO, and ethylene, CH₂=CH₂ production become evident, while the production of CO₂ and CO decrease. Since the stoichiometric α-Fe₂O₃(10-12) surface exposes cations and anions with a single coordination vacancy, the decrease in oxygen-containing products with surface reduction is attributed to a decrease in the availability of coordinately-unsaturated surface oxygen anions. The selectivity change to coupling products for the most reduced surfaces is attributed to the appearance of surface cations with multiple coordination vacancies associated with the loss of surface oxygen.