The electronic structure of stoichiometric and reduced CeO2 surfaces: an XPS, UPS and HREELS study

Pfau, A.; Schierbaum, K.D.

doi:10.1016/0039-6028(94)90027-2

Cited by 638 publications

(470 citation statements)

References 16 publications

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“…Overall, these calculations give lattice parameters within 1% of the experimental values, slightly improving over the DFT(+U) results. The calculated electronic structures, i.e., the band dispersions and the position of the empty Ce 4f and Ce 5d bands with respect to the occupied O 2p bands are also in good agreement with experimental data [19][20][21][22][23].…”

Section: Introductionsupporting

confidence: 80%

“…For the Ce 4f-Ce 5d separation, the experimental result of ~3.0 eV is less clear due to the large broadening of the signal. The experimental values were obtained using a combination of photoemission and inverse photoemission, as well as absorption spectroscopy [19][20][21][22]. …”

Section: The Formation Energy Of An Oxygen Vacancy In Charge Statementioning

confidence: 99%

“…CeO 2 is an insulator with a large band gap [19][20][21][22][23]. The electronic structure of CeO 2 has been probed by different experimental techniques, including valence x-ray photoemission spectroscopy (XPS) [19][20][21][22], O 1s x-ray absorption spectroscopy (XAS) [20], electron energy loss spectroscopy (EELS) [20,21], and optical reflectance (OR) [23].…”

Section: Introductionmentioning

confidence: 99%

“…The electronic structure of CeO 2 has been probed by different experimental techniques, including valence x-ray photoemission spectroscopy (XPS) [19][20][21][22], O 1s x-ray absorption spectroscopy (XAS) [20], electron energy loss spectroscopy (EELS) [20,21], and optical reflectance (OR) [23]. The valence band, composed of O 2p states is separated by a gap of ~3 eV from a quite narrow unoccupied band composed of Ce 4f states.…”

Section: Introductionmentioning

confidence: 99%

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Disentangling the role of small polarons and oxygen vacancies in CeO2

et al. 2017

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The outstanding performance of cerium oxide (CeO 2 ) as ion conductor or catalyst strongly depends on the ease of Ce 4+ ↔Ce 3+ conversion and oxygen vacancyformation. An accurate description of Ce 3+ and oxygen vacancy is therefore essential to further progress in this area. Using the HSE06 hybrid functional, we investigate the formation and migration of small polarons (Ce 3+ ) and their interaction with oxygen vacancies in CeO 2 , considering the small polaron and vacancy as independent entities.Oxygen vacancies are double donors and can bind up to two small polarons, forming a positively charged or neutral complex. We compute the electron self-trapping energy (i.e., energy gain when forming a small polaron), the small-polaron migration barrier, vacancy formation and migration energies, and vacancy-polaron binding energies. We find that small polarons weakly bind to oxygen vacancies, yet this interaction significantly contributes to the activation energy for hopping electronic conductivity.The results are compared with previous calculations and discussed in the light of available experimental data.

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Section: Introductionsupporting

confidence: 80%

Section: The Formation Energy Of An Oxygen Vacancy In Charge Statementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Disentangling the role of small polarons and oxygen vacancies in CeO2

et al. 2017

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“…X-ray photoelectron spectroscopy (XPS) is the method that allows monitoring changes in the local environment of ions and their oxidations states [17]. The surface chemical states of Ce cations have been explored so far preferably for undoped CeO 2 [18][19][20][21][22][23], CeO 2 -based solid solutions [24][25][26], and composites composed of CeO 2 and transition metals or their oxides [27][28][29][30][31][32][33][34]. It was shown that properties of composite materials (redox properties, formation of surface and bulk oxygen vacancies, oxygen storage and release) can be optimised through the variation of the CeO 2 /Me(Me x O y ) ratios.…”

Section: Introductionmentioning

confidence: 99%

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Konysheva

Francis

2013

Applied Surface Science

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Keywords:X-ray photoelectron spectroscopy (XPS) Surface composition Composites with perovskite and fluorite structures Oxidation state of cerium cations Binding energy a b s t r a c t X-ray photoelectron spectroscopy (XPS) has been used to explore the cation rearrangement between the surface and bulk of grains and the surface chemical states of Ce, Mn, Co, Sr, and O ions in the single phase CeO 2 -based solid solutions and in the two phase (100 − x)La 0.6 Sr 0.4 CoO 3 -xCeO 2 (LSCCx) and (100 − x)La 0.8 Sr 0.2 MnO 3 -xCeO 2 (LSMCx) composites. The well-resolved Ce 3d 5/2 and Ce 3d 3/2 spin-orbit components were determined to study the Ce 4+ to Ce 3+ electronic transition at the surface. The surface of the LSCCx and LSMCx (x = 8-40 mol%) composites is depleted in cerium. Both Ce 4+ and Ce 3+ cations were revealed. The surface fraction of Ce 4+ cations increases with the rise in CeO 2 content in both systems, but it is higher by about a factor of two in the LSCC composites. A strong enrichment of the surface by Co cations was observed for the composites LSCCx (x = 8-40 mol%), implying that the presence of cerium could facilitate the Co surface segregation. A slight Sr surface enrichment compared to the nominal stoichiometry was found for La 0.6 Sr 0.4 CoO 3 , CeO 2 -based solid solutions, LSCC57, and LSMCx (x = 10-57) composites. In contrast, the surface of the LSCCx (x = 10-37) composites is slightly depleted in strontium cations. The O 1s spectra of the LSCC and LSMC composites contain several contributions associated with the lattice oxygen related to the phases with the perovskite and fluorite structures as well as with different surface states. Their contributions vary with CeO 2 content and a chemical origin of the transition metal cations on the B-site in the perovskite structure. The Ce 2 (CO 3 ) 3 -based phase seems to exist at the surface of grains and crystallites in the LSCC57 and LSCM composites.

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Oxidative Inorganic Multilayers for Polypyrrole Film Generation

Salomäki

Räsänen

Leiro

et al. 2010

Adv Funct Materials

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A controlled nanoscale fabrication of conducting polymer films sets severe requirements for the preparation method and substrate. A new and versatile approach for producing thin polypyrrole films on a variety of surfaces is presented. Purely inorganic thin films are first prepared from poly(metaphosphate) and tetravalent metal ions using a sequential layer‐by‐layer technique. Redox‐active cerium(IV) polyphosphate multilayer and redox‐inactive zirconium(IV) and hafnium(IV) polyphosphate multilayers are prepared. Cerium‐based polyphosphate films grow exponentially with the number of layers but multilayers containing zirconium or hafnium exhibit a linear buildup process. All the studied systems produce relatively smooth films with initial bilayer thickness less than 2 nm. The cerium(IV) containing film is redox‐active, which is shown by its capability to form a polypyrrole layer on its surface by oxidation of pyrrole monomers in the adjacent aqueous solution. This is a general method to produce thin oxidative films of arbitrary size and form on a wide variety of surfaces.

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The electronic structure of stoichiometric and reduced CeO2 surfaces: an XPS, UPS and HREELS study

Cited by 638 publications

References 16 publications

Disentangling the role of small polarons and oxygen vacancies in CeO2

Disentangling the role of small polarons and oxygen vacancies in CeO2

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Oxidative Inorganic Multilayers for Polypyrrole Film Generation

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