Oxidized Ni Nanostructures Supported by Mesoporous Al₂O₃ : Relationship between the Structure and Reactivity for CO Oxidation Studied via Photoemission Spectroscopy

Oxidized Ni, at very small loadings, was deposited on mesoporous Al₂O₃ using atomic layer deposition. The prepared structures were used as catalysts for CO oxidation between 30 and 250 .deg. C. Ni particles with a mean size less than 1–2 nm were shown to be reactive, even at room temperature, for CO oxidation. The room temperature reactivity for CO oxidation was decreased with increasing reaction time. However, when post-annealing at 300 .deg. C was applied to deactivated catalysts, a higher initial CO oxidation reactivity (compared with the value of the preceding catalytic operation) was observed. Furthermore, we observed that repeated cycles of room-temperature CO oxidation and post-annealing at 300 .deg. C gradually increased the catalytic activity for room temperature CO oxidation. X-ray photoelectron spectroscopy was used to determine the origin of this behavior and the results are discussed in detail.