Comparative XPS study of surface reduction for nanocrystalline and microcrystalline ceria powder

Qiu, Limei; Liu, Fen; Zhao, Lei; Ma, Ying; Yao, Jiannian

doi:10.1016/j.apsusc.2005.07.024

Cited by 197 publications

(94 citation statements)

References 15 publications

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“…Concentration of the dopant elements in the nanoparticles is determined from the XPS data. Given that there is some ambiguity over the accuracy of the calculated ionization state of cerium, this technique was not used to quantify the concentration of Ce ?4 and Ce ?3 in the nanoparticle samples (Qiu et al 2006), but is used as a qualitative confirmation of the trends determined from an analysis of the data collected using the other characterization equipment.…”

Section: Methodsmentioning

confidence: 99%

Control of oxygen vacancies and Ce+3 concentrations in doped ceria nanoparticles via the selection of lanthanide element

et al. 2012

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The effect of lanthanides that have positive association energies with oxygen vacancies, such as samarium and neodymium, and the elements with negative association energies, such as holmium and erbium, on ionization state of cerium and, consequentially, the oxygen vacancy concentration in doped ceria nanoparticles are investigated in this article. Structural and optical characterizations of the doped and undoped ceria nanoparticles, synthesized using chemical precipitation, are carried out using transmission electron microscopy, X-ray diffractometry, optical absorption spectroscopy, and fluorescence spectroscopy. It is deduced that the negative association energy dopants decrease the conversion of Ce ?4 into Ce ?3 and, hence, scavenge the oxygen vacancies, evidenced by the observed increase in the allowed direct bandgap, decrease in the integrated fluorescence intensity, and increased the size of doped nanoparticles. The opposite trends are obtained when the positive association dopants are used. It is concluded that the determining factor as to whether a lanthanide dopant in ceria acts as a generator or scavenger of oxygen vacancies in ceria nanoparticles is the sign of the association energy between the element and the oxygen vacancies. The ability to tailor the ionization state of cerium and the oxygen vacancy concentration in ceria has applications in a broad range of fields, which include catalysis, biomedicine, electronics, and environmental sensing.

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Section: Methodsmentioning

confidence: 99%

Control of oxygen vacancies and Ce+3 concentrations in doped ceria nanoparticles via the selection of lanthanide element

et al. 2012

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“…Moreover, Ce 3d peak at 885.7 eV assignable to the Ce 3d 5/2 4f 1 of Ce(III) was also observed. The occurrence of Ce(III) species on the surface of bulk Ce(IV) species, which was caused by X-ray irradiation, is widely reported in the literatures [28,29]. Similarly, the surface Ce(III) species detected in our XPS test were also likely to be caused by the X-ray irradiation and deposited Ce(OH) 3 that was not oxidized during the passivation treatment.…”

Section: X-ray Photoelectron Spectroscopy (Xps)mentioning

confidence: 47%

Preparation of Ce-modified Raney Ni Catalysts and Their Application in Aqueous-Phase Reforming of Cellulose

Wen

Wang

et al. 2011

Catal Lett

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A series of Ce-modified Raney Ni (RNi) catalysts were successfully prepared by a simple wet chemical route and employed in aqueous-phase reforming of cellulose. Remarkable enhancement in hydrogen selectivity and yield after the Ce introduction was observed. At 533 K and autogenous pressure, a highest hydrogen yield of 17.8 mmol/g cellulose , which was comparable with that of 5 wt% Pt/AC, could be obtained over Ce-modified catalyst at a Ce:Ni ratio of 0.054. The catalysts were characterized by N 2 adsorption/desorption, XRD, SEM, XPS and H 2 -TPD. It was found that cerium existed at the surface of the catalyst as Ce(OH) 3 , and more defects were generated during Ce modification. Based on the characterization and catalytic performance, it was suggested that the deposited Ce(OH) 3 may transform into reducible CeO 2 under the reaction conditions, thus promoting the desired water-gas shift reaction, leading to more H 2 . On the other hand, the active sites for undesired methanation reaction may be effectively poisoned by Ce modification, thus leading to less undesired methane.

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“…It is reported that the intensity of the doublet v/u is positively correlated with the concentration of Ce 3+ ions in CeO 2 . 20 Therefore, the Ce 3+ concentration in the 550 • C-annealed CeO 2 film is much higher than that in the 450 • C-annealed one. Actually, the formation of Ce 3+ ions is closely correlated with the existence of oxygen vacancies, which can be understood according to the Kroger-Vink notation 4Ce 4+ + O 2− → 2Ce 4+ + 2Ce 3+ + V O + (1/2)O 2 (g), where V O refers to oxygen vacancy.…”

Section: Resultsmentioning

confidence: 99%

“…It has been documented that the Ce 3d XPS spectrum of CeO x (x≤2) can be assigned to six peaks of three spin-orbit doublets. [20][21][22] Fig. 2(c).…”

Section: Resultsmentioning

confidence: 99%

Ultraviolet-visible electroluminescence from metal-oxide-semiconductor devices with CeO2 films on silicon

Zhu

Wang

et al. 2015

AIP Advances

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We report on ultraviolet-visible (UV-Vis) electroluminescence (EL) from metal-oxide-semiconductor (MOS) devices with the CeO2 films annealed at low temperatures. At the same injection current, the UV-Vis EL from the MOS device with the 550 °C-annealed CeO2 film is much stronger than that from the counterpart with the 450 °C-annealed CeO2 film. This is due to that the 550 °C-annealed CeO2 film contains more Ce3+ ions and oxygen vacancies. It is tentatively proposed that the recombination of the electrons in multiple oxygen-vacancy–related energy levels with the holes in Ce 4f1 energy band pertaining to Ce3+ ions leads to the UV-Vis EL.

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Comparative XPS study of surface reduction for nanocrystalline and microcrystalline ceria powder

Cited by 197 publications

References 15 publications

Control of oxygen vacancies and Ce+3 concentrations in doped ceria nanoparticles via the selection of lanthanide element

Control of oxygen vacancies and Ce+3 concentrations in doped ceria nanoparticles via the selection of lanthanide element

Preparation of Ce-modified Raney Ni Catalysts and Their Application in Aqueous-Phase Reforming of Cellulose

Ultraviolet-visible electroluminescence from metal-oxide-semiconductor devices with CeO2 films on silicon

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