Raman Spectra of Polycrystalline CeO₂: A Density Functional Theory Study

Abstract

Cerium oxide is an important material for catalytic and fuel cell applications. We present an ab initio density functional theory (DFT) study of the vibrational properties of ceria focusing on the interpretation of Raman spectra of polycrystalline powder samples, with vibrational bands in the frequency region between 250 and 1200 cm −1 . The model systems include the oxidized CeO 2 as well as the reduced CeO 2−x and Ce 2 O 3 bulk materials together with the CeO 2 (111) and oxygen defective CeO 2−x (111) surfaces. The experimentally observed band at 250 cm −1 is assigned to a surface mode of the clean CeO 2 (111) surface, in agreement with our Raman spectra of ceria (CeO 2 ) powders with varying crystal size (Filtschew, A.; Hofmann, K.; Hess, C., J. Phys. Chem. C 2016, 120, 6694). The reduced model systems display signature vibrational bands in the 480−600 cm −1 region associated with the presence of oxygen defects and reduced Ce 3+ ions. In the high-frequency region between 800 and 900 cm −1 , characteristic peroxide (O 2 2−) stretching vibrations at the oxidized and defective ceria surfaces are obtained, and a systematic study with respect to the peroxide coverage provides the basis for a correlation between the position of the peroxide stretching mode and its adsorption geometry and concentration. The present theoretical analysis allows for a consistent description of the experimental Raman spectra of polycrystalline ceria. The outlined approach serves as a reference for the description of vibrational properties of other metal oxides.

Synthesis and Characterization of Bismuth-Cerium Oxides for the Catalytic Oxidation of Diesel Soot

“…Note that with "x" we denote in the following that the amount of oxygen is variable and depending on preparation conditions, whereas the other subscripts in the all formulae represent the molar composition. The band at ν = 462 cm −1 was attributed to the F 2g mode of CeO 2 [26]. This confirms that the pure CeO 2 was synthesized in both cases without any defect structure.…”

“…For the Ce 0.0 Bi 1.0 O x (pure bismuth(III) oxide) all bands typical for α-Bi 2 O 3 were observed for both synthesis methods. These bands were the following one: ν = 120 cm −1 , 140 cm −1 , 152 cm −1 , 184 cm −1 , 212 cm −1 , 281 cm −1 , 314 cm −1 , 411 cm −1 , 449 cm −1 , and 532 cm −1 [26][27][28][29]. For both synthesis routes, with increasing Ce content the F 2g band of CeO 2 dominates the Raman spectra but with a higher F 2g band FWHM (full width at half maximum, see supplementary information Table S1) was attributed to the F2g mode of CeO2 [26].…”

“…Areas with predominantly α-Bi 2 O 3 and areas with β-Bi 2 O 3 mixed with CeO 2 were observed. The F 2g band of CeO 2 at ν = 464 cm −1 and the band of β-Bi 2 O 3 at ν = 466 cm −1 are overlapping [26,29]. Therefore, it is hardly possible to distinguish between CeO 2 and β-Bi 2 O 3 in the range of high Bi content.…”

Facile Synthesis and Electrochemical Properties of Perovskite‐type CeMnO3 Nanofibers

“…The vibrational modes of CeMnO 3 NFs and CeO 2 NFs were illustrated by Raman spectra, as shown in Figure (c). The dominant peak at 460 cm −1 in CeO 2 NFs is assigned to the first‐order F 2g (υ F2g , Fm3 m group) symmetric stretching of oxygen atoms around cerium ions in CeO 2 with fluorite structure . Two main peaks at 458 and 654 cm −1 can be clearly seen in CeMnO 3 NFs sample.…”

Organic inclusions evidence, composition, and cathodoluminescence behaviour for the formation conditions of fluorapatite from Anemzi (Morocco)

“…The other Raman bands of around 605–429 cm −1 are attributable to the PO 4 3− bending modes . The band at 266 cm −1 can be due to the presence of La and Ce in the structure of fluorapatite . The slightly elevated background indicates the presence of luminescence impurities and/or complex defects in the mineral structure .…”