Oxidation of CO on Fe2O3 model surfaces

Using first principles calculations based on a gradient corrected density functional formalism we show that Fe₂O₃ nano-particles with (1 0 0) and (0 0 0 1) surface orientations can oxidize CO to form CO₂ with or without the presence of O₂. However, depending on the surface orientation, the oxidation occurs through differing sequences. On the (1 0 0) surface, in the absence of O₂, two CO molecules are required for one CO oxidation in a concerted reaction while on a oxygen terminated (0 0 0 1) surface, a single CO molecule itself, without the aid of a second CO, can react with the lattice oxygen atoms to form CO₂. In the presence of O₂, the O vacancies created by an initial oxidation through lattice oxygen act as the favored sites for O₂ adsorption which can subsequently oxidize the incoming CO. Detailed reaction paths and the corresponding energetics for the proposed mechanisms are also studied.