Synthesis and Characterization of Ce_1−xEu_xO_2−x/2 Mixed Oxides and Their Catalytic Activities for CO Oxidation

Abstract

A series of Ce1−x Eu x O2−x/2 mixed oxides was synthesized by coprecipitation. The solids were characterized by means of XRF, SBET, XRD, UV−vis, and Raman techniques, and their catalytic activities toward CO oxidation were tested. A solid solution, with CeO2 F-type structure, is formed for europium contents (measured as Eu2O3 by XRF) ≤20% wt. For higher contents, the solid solution is not formed, but a physical mixture is detected. The existence of oxygen vacancies in the solids with Eu2O3 contents between 3 and 17% wt was demonstrated by the presence of bands at 532 and 1275 cm−1 in their Raman spectra. The catalytic performances of the solids correlate with the amount of these punctual defects in the solid solution.

Synergy between gold and oxygen vacancies in gold supported on Zr-doped ceria catalysts for the CO oxidation

“…The surface character of most of oxygen vacancies which were detected for the Ce-Zr mixed oxides through the Raman spectra has been previously suggested for a similar system (Eu-doped ceria [43]) evaluated under the same experimental conditions that our material. In this work it was considered that using a laser line where the optical absorption exists, the majority of excitation laser and scattering light were adsorbed by the sample.…”

“…In good agreement with our results, the enhancement of the catalytic activity in CO oxidation reactions by doping the structure of CeO 2 has been widely evidenced by many authors applying several doping agents: Zn [63], Sm [22], Fe [64], Co, Mn [65], Cu [66,67] and Eu [43], among others. In these works, the creation of oxygen vacancies by the strong interaction of the CeO 2 framework and the doping cation is commonly proposed as a determinant structural effect that facilitates the adsorption and activation of the CO and O 2 molecules during the catalytic reaction.…”

“…As presented in recent works, a correct evaluation of the evolution of oxygen vacancies population in pure and doped cerium oxides must be carried out by comparing the area ratio of the oxygen vacancies band and the F 2g signal (Ov/F 2g ) [8,42,43] in order to reduce the possible influence of the particle size and other effects over the shape and intensity of the signals [8,43,46,47]. The Figure 5 inset shows how the population of oxygen vacancies increases with the Zr At.% in our materials.…”

Gold supported on CuOx/CeO2 catalyst for the purification of hydrogen by the CO preferential oxidation reaction (PROX)

“…The CeCu presents the typical signals of CeO 2 [14,37,49,50]. The most intense one, centered at 463 cm -1 , corresponds to the F 2g band and the signal at 612 cm -1 is due to the presence of oxygen vacancies (Ov).…”

The nature of oxygen states on the surfaces of CeO2 and La-doped CeO2

“…Trivalent rare-earth cations have been shown to be effective for catalysis, [21] with La(III) being a promising candidate dopant. [6] It is generally considered that when CeO 2 is doped with a trivalent cation, such as La(III), two lattice Ce(IV) ions are replaced by the dopants and an O ion is removed to conserve the charge.…”