In situ fabrication of Ce1−xLaxO2−δ/palygorskite nanocomposites for efficient catalytic oxidation of CO: effect of La doping

Abstract

Novel palygorskite (PG) supported Ce_1−xLa_xO_2−δ nanocomposites were prepared by a facile in situ deposition method using hexamethylenetetramine as the precipitant. The textural and structural properties of the products were characterized by XRD, HRTEM, FT-IR, Raman, XPS and TPR techniques. The results indicated that the oxide particles with an average size of about 5 nm were loaded successfully onto the surface of PG rods and were uniformly dispersed. The catalytic activities of Ce_1−xLa_xO_2−δ/PG (x from 0.1 to 0.9) for CO oxidation were investigated. La³⁺ doping was found to have critical effects on the CO oxidation activity. The best Ce_1−xLa_xO_2−δ/PG nanocomposite was obtained when the x value was adjusted to 0.5, and the reaction rate was found to be three times higher than that of a commercial CeO₂ catalyst. Adequate introduction of La³⁺ promotes the formation of non-stoichiometric Ce_1−xLa_xO_2−δ and is responsible for the formation of oxygen vacancies and surface superoxide ions. However, when the doping ratio increases to 0.6 or higher, co-precipitation of La₂O₃ leads to decreased redox properties and CO oxidation activity.