UV and Visible Raman Studies of Oxygen Vacancies in Rare-Earth-Doped Ceria

Abstract

Surface properties of rare-earth (RE) doped ceria (RE = Sm, Gd, Pr, and Tb) were investigated by UV (325 nm) and visible (514, 633, and 785 nm) Raman spectroscopy, combined with UV-vis diffuse reflectance spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectra techniques. It was found that the optical absorption property of samples, the wavelength of detecting laser line, and the inhomogeneous distribution of the dopants significantly affected the obtained surface information, namely, the peak intensity and shape at ca. 460 and 570 cm(-1), as well as the observed oxygen vacancy concentration (A(570)/A(460)). The UV laser line detected the surface information of RE-doped ceria and disclosed the presence of many oxygen vacancies in the samples. The visible laser lines penetrated into the inner layer of the Sm- or Gd-doped CeO(2) and reflected the whole information of samples because of their weak absorptions of the visible laser. However, the Pr- or Tb-doped CeO(2) absorbed visible light strongly; thus, the laser can only determine the outer surface information of the sample.

Synthesis and application of rare-earth elements (Gd, Sm, and Nd) doped ceria-based solid solutions for methyl mercaptan catalytic decomposition

“…2, the lattice parameter 'a' of the RE doped ceria samples, calculated by using the relevant equations from previous documents [20,21], has been observed to increase with an increase in the introduced RE cations size. Surprisingly, the trend of this variation is almost linear, which indicates that there is a specific interaction between ceria and the doped RE oxides [12], and further confirming the formation of solid solutions [19]. Additionally, previous research suggested that the change of ceria lattice was closely related to the crystallite size of the catalyst and the lattice defects (especially for oxygen vacancies) concentration in the catalyst [23].…”

“…1(A), it is observed that all the samples exhibit typical fluorite-like cubic structure of CeO 2 corresponding to (111), (200), (311), (222), (400), (331) and (420) planes. Besides, no diffraction peaks of other RE oxides are found, which indicates that RE ions are incorporated into CeO 2 lattice and several homogeneous solid solutions may be formed [19].…”

Influence of isovalent and aliovalent dopants on the reactivity of cerium oxide for catalytic applications

“…For the Eu case, the observed binding energy is 1134 eV, which corresponds to +3 oxidation states in CE material [41]. As for the Sm, a peak was identified in the range of ∼1082.1-1083.2 eV, which indicates presence of Sm 3+ in the CS sample [42]. This Fig.…”

Effect of Reduction Treatment on CO Oxidation with CeO2 Nanorod‐Supported CuOx Catalysts

“…In Figure 6a,t he CeO 2 nanorods exhibit the first-order F 2g peak near 461 cm À1 .T he Raman bands at 262 and 602 cm À1 have been reported to be associated with oxygen vacanciesi nC eO 2 . [29] The monoclinic CuO exhibits five major Ramanb ands at 275, 506, 622, 1086, and 1241 cm À1 in the range between 200 and 1300 cm À1 (Figure 6d). These five bands can also be observed in both 10 wt %C uO-CeO 2 and reduced 10 wt %C uO x -CeO 2 samples with ar elatively similari ntensity.M etallic Cu is not Raman active therefore all Raman bands are attributed to CeO 2Àx (0 x 0.5) and CuO x (0 < x 1).…”