Compositional heterogeneity in ceria-based mixed oxides observed by x-ray photoelectron spectroscopy

Graham, George W.; Roe, Charles L.; Haack, Larry P.; Straccia, A. M.

doi:10.1116/1.582305

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

2000

DOI: 10.1116/1.582305

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Compositional heterogeneity in ceria-based mixed oxides observed by x-ray photoelectron spectroscopy

George W. Graham

Charles L. Roe

Larry P. Haack

et al.

Abstract: Articles you may be interested inPt metal-CeO 2 interaction: Direct observation of redox coupling between Pt 0 / Pt 2 + / Pt 4 + and Ce 4 + / Ce 3 + states in Ce 0.98 Pt 0.02 O 2 − δ catalyst by a combined electrochemical and x-ray photoelectron spectroscopy study Stability of cerium oxide on silicon studied by x-ray photoelectron spectroscopy

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Cited by 6 publications

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“…Surface compositions in cerium and zirconium were determined by peak integration of Ce 3d and Zr 3p for the each mixed-oxide FSP series and four CP solids (SI). We found that for all solids, the estimated binding energies (181.85 +/-0.05 for Zr 3d and 882.2 +/-0.2 for Ce 3d ) are similar to values reported in the literature[57]…”

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confidence: 85%

Surface effect of nano-sized cerium-zirconium oxides for the catalytic conversion of methanol and CO2 into dimethyl carbonate

Daniel

Schuurman

Farrusseng

2021

Journal of Catalysis

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The direct synthesis of Dimethyl carbonate (DMC) from methanol and CO 2 is a green process which allows CO 2 valorization. Among efficient catalysts, ceria, zirconia and cerium-zirconium mixed oxides are often reported as the most active catalysts. In a recent report, we discovered that ceriumzirconium mixed oxides prepared by Flame Spray Pyrolysis (FSP) show greater catalytic activities than those prepared by precipitation, although both exhibit very similar surface area and bulk features.The objective of this study was to find out the origins of the superior catalytic activities obtained by flame spray pyrolysis synthesis method by a deeper analysis of bulk and surface properties. We have opted to focus on mixed ceria-zirconia of equimolar composition (Ce 0.5 Zr 0.5 O 2 ) as it exhibits maximum catalytic activity for both synthesis methods. Combining bulk and surface characterization as well as surface adsorption measurements using probe molecules, we propose that flame spray pyrolysis enables a surface enrichment in cerium oxide still in interaction with zirconium oxide that leads to a high concentration of adsorbed methanol at the surface, which might explain the greater activity of the catalysts prepared using this method. Beyond the application of DMC synthesis, we can anticipate that Flame Spray Pyrolysis synthesis should generate relative high surface area mixed oxides with different catalytic performances with respect to mixed oxides prepared at lower temperature owing their metastable nature.

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supporting

confidence: 85%

Surface effect of nano-sized cerium-zirconium oxides for the catalytic conversion of methanol and CO2 into dimethyl carbonate

Daniel

Schuurman

Farrusseng

2021

Journal of Catalysis

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Automotive catalytic converters: current status and some perspectives

2003

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Spectroscopic Characterization of Heterogeneity and Redox Effects in Zirconium−Cerium (1:1) Mixed Oxides Prepared by Microemulsion Methods

et al. 2003

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Two Zr-Ce (1:1 molar ratio) mixed oxide specimens, made by the same microemulsion method from different cerium precursor salts (samples ZC1 and ZC2), have been studied by a combination of physicochemical techniques. After calcination at 773 K (high surface area materials HS: S BET ) 96 ( 1 m 2 g -1 ) both samples present similar characteristics in XRD, Raman and TEM (pseudocubic phase t′′), and XPS/Ar + -etching experiments. This latter evidence for those materials gives a similar moderate surface enrichment in cerium and a surface anion vacancy concentration (judged from O(1s) peak shifts) lower than in CeO 2 ; the latter effect suggests an easy diffusion of vacancies to bulk or subsurface regions. Only EPR of adsorbed superoxide species detects a difference between both samples, evidencing in ZC2-HS the presence of small, more reducible Ce-rich bidimensional patches over a Zr-richer substrate. According to XPS/Ar + etching profiles, by calcination at 1173 K (LS materials; S BET < 8 m 2 g -1 ), surface segregation of small (ca. 3 nm) Ce-rich particles, not yet distinguishable by Raman or diffraction data and able to sustain at the surface local anion vacancy concentrations higher than in the other specimens (closer to the behavior of pure CeO 2 ), occurs on the ZC2 material; the ZC1 specimen, in contrast, actually becomes more homogeneous upon calcination at 1173 K. The short-scale heterogeneity indicated by EPR for sample ZC2-HS, and not for ZC1-HS, is presumed to act as a nucleus favoring formation of this new phase upon calcination. The data obtained evidence the ability of EPR and XPS/Ar + -etching methods to reveal in these materials heterogeneity differences, not detectable by the other techniques, leading to higher reducibility of the Ce-rich surface domains in the ZC2 materials. The results are discussed in connection with the oxygen storage and buffering properties of these mixed oxides.

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Compositional heterogeneity in ceria-based mixed oxides observed by x-ray photoelectron spectroscopy

Cited by 6 publications

References 2 publications

Surface effect of nano-sized cerium-zirconium oxides for the catalytic conversion of methanol and CO2 into dimethyl carbonate

Surface effect of nano-sized cerium-zirconium oxides for the catalytic conversion of methanol and CO2 into dimethyl carbonate

Automotive catalytic converters: current status and some perspectives

Spectroscopic Characterization of Heterogeneity and Redox Effects in Zirconium−Cerium (1:1) Mixed Oxides Prepared by Microemulsion Methods

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