Valence of Highly Dispersed Cerium Oxide Species on Silica Quantitatively Estimated by Ce L<SUB>III</SUB>-edge XANES

Abstract

A series of silica-supported cerium oxide samples having various cerium content were prepared by conventional impregnation method, followed by calcination in air. Ce L III -edge XANES study revealed that highly dispersed cerium oxide species on silica surface were predominantly in trivalent oxidation state and cerium oxide nano-particles on silica contain mainly tetravalent cation like as CeO 2 bulk oxide. This elucidated that UV absorption band at 265 nm is assignable to Ce(III) species dispersed on silica.

Chemical and Electronic Changes of the CeO2 Support during CO Oxidation on Au/CeO2 Catalysts: Time-Resolved Operando XAS at the Ce LIII Edge

“…X-ray absorption spectroscopy (XAS) measurements in the near edge region (XANES) spectra recorded at the Ce LIII edge (measured at 80 °C in N2): (a) of the Ce (III) reference (Ce2(CO3)3 × H2O, red line); (b) of the Ce(IV) reference (CeO2) (blue line) and reference data published by Ravel and co-workers (orange lines) [44]. The dashed curves represent the main individual components of Ce as published by Yoshida et al [45], the solid black lines denote a fit based on these components to our data. For an acceptable agreement with our Ce(IV) reference (blue) the component marked in red, which represents the white line in Ce (III), had to be increased in intensity compared to the fit to Ce(IV) data published by Yoshida (black).…”

“…Furthermore, the inflection point of the spectrum of Ce(IV) is located at about 1.0 eV higher energy compared to that of the reduced Ce(III) species (5725.6 eV). The main contributions to the respective XANES spectra, which are indicated as dashed and dotted lines in the spectra shown in Figure 1 [45], are summarized in Table 1. A detailed discussion of the respective electronic states and transitions contributing to the spectra was given by Yoshida et al [45].…”

“…The main contributions to the respective XANES spectra, which are indicated as dashed and dotted lines in the spectra shown in Figure 1 [45], are summarized in Table 1. A detailed discussion of the respective electronic states and transitions contributing to the spectra was given by Yoshida et al [45]. The solid black lines represent the fits based on these components to our reference spectra.…”

“…Table 1. Overview of the individual contributions (peak heights and energy of Lorentzian) to the normalized XANES spectra of our references at the Ce L III absorption edge, with the peaks and peak positions taken from [45]. The respective initial and final states are discussed in that reference.…”

Structural studies of mesoporous ZrO2-CeO2 and ZrO2-CeO2/SiO2 mixed oxides for catalytical applications

“…The peak C occurs due to dipole transitions and it is characteristic of the Ce trivalent state. The pre-edge peak D corresponds to multiple scattering processes [35,36,37,38].…”