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 °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 °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 °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.