Mobility of oxygen and catalytic properties of rare earth oxides with respect to oxidation of hydrogen

Antoshin, G. V.; Миначев, Х. М.; Dmitriev, R. V.

doi:10.1007/bf00906841

Cited by 23 publications

(45 citation statements)

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“…7͑b͔͒. In support of this hypothesis, praseodymium oxide was reported to have the maximum activity in isotopic exchange with molecular oxygen among the RE oxides; 54 19 It must, however, be pointed out that these theoretical calculations apply to the zero temperature/pressure limit and that they refer to bulk materials without considering the properties of thin films under heteroepitaxy constraints ͓indeed, hex-Pr 2 O 3 almost perfectly matches Si͑111͒ ͑ϳ+ 0.5% ͒ but its misfit to Ge ͑ϳ−3.6% ͒ is comparable to the direct mismatch of Ge with respect to Si ͑ϳ4.2% ͒; on the contrary, cub-Pr 2 O 3 represents a more appropriate buffer because its lattice is ϳ2.7% bigger than two times the Si lattice and ϳ1.4% smaller than two times the Ge lattice͔. At this step, no further O is available anymore in the Pr oxide ͓as represented by the absence of the dashed arrow in picture 7͑d͔͒.…”

Section: Discussionmentioning

confidence: 85%

The influence of lattice oxygen on the initial growth behavior of heteroepitaxial Ge layers on single crystalline PrO2(111)∕Si(111) support systems

Giussani

Seifarth

Rodenbach

et al. 2008

Journal of Applied Physics

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A combined structure and stoichiometry study on the growth behavior of single crystalline Ge(111) layers on PrO2(111)∕Si(111) heterostructures is presented. Ex situ x-ray diffraction techniques indicate that the interaction between Ge and PrO2(111) results in a complete reduction of the buffer oxide to a cubic Pr2O3(111) film structure. In situ reflection high energy electron diffraction, x-ray and ultraviolet photoelectron spectroscopy studies demonstrate that this chemical reduction of the oxide support occurs during the initial Ge growth stage. The interaction of PrO2 with Ge results in the formation of an amorphous Ge oxide layer by the diffusion of lattice oxygen from the dielectric to the forming semiconductor deposit. After the complete conversion of PrO2 to cubic Pr2O3, the supply of reactive lattice oxygen is exhausted and the continuous Ge deposition reduces the initially formed amorphous GeO2-like film to GeO. The sublimation of volatile GeO uncovers the single crystalline cubic Pr2O3(111) film surface which provides a thermodynamically stable template for elemental Ge heteroepitaxy. A Volmer–Weber growth mode is observed which results after island coalescence in the formation of atomically smooth, single crystalline Ge(111) layers.

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Section: Discussionmentioning

confidence: 85%

The influence of lattice oxygen on the initial growth behavior of heteroepitaxial Ge layers on single crystalline PrO2(111)∕Si(111) support systems

Giussani

Seifarth

Rodenbach

et al. 2008

Journal of Applied Physics

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“…The Pr 3d signal recorded after the plasma treatment [ Fig. 3(b)] clearly shows that previous spectra of PrO 2 did not represent stoichiometric but indeed most probably a reduced PrO 2 . To better illustrate the various contributions, the spectrum was analyzed using a curve fitting routine with a Voigt profile (Fitt 1.2 by Hyun-Jo Kim, Seoul National University).…”

Section: A Xps Analysismentioning

confidence: 97%

Photoemission study of praseodymia in its highest oxidation state: The necessity of in situ plasma treatment

Schaëfer

Gevers

Zielasek

et al. 2011

The Journal of Chemical Physics

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A cold radio frequency oxygen plasma treatment is demonstrated as a successful route to prepare clean, well-ordered, and stoichiometric PrO 2 layers on silicon. High structural quality of these layers is shown by x-ray diffraction. So far unobserved spectral characteristics in Pr 3d x-ray photoelectron (XP) spectra of PrO 2 are presented as a fingerprint for praseodymia in its highest oxidized state. They provide insight in the electronic ground state and the special role of praseodymia among the rare earth oxides. They also reveal that former XP studies suffered from a significant reduction at the surface.

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“…No direct measurement of the heat of oxygen desorption for CeO 2 could be found. Instead the heat of desorption for CeO 2 was estimated from the reported 67 kJ/mol activation energy in isotopic 16 O 2 / 18 O 2 exchange [50] according to the Brønsted-Evans-Polanyi relationship obtained by Boreskov [46]. However, it must be added that significant ambiguity exists for exchange on ceria with reported activation energies in the 67-131 kJ/mol range [29,[50][51][52].…”

Section: Sources For the Heat Of Oxygen Chemisorptionmentioning

confidence: 99%

“…Instead the heat of desorption for CeO 2 was estimated from the reported 67 kJ/mol activation energy in isotopic 16 O 2 / 18 O 2 exchange [50] according to the Brønsted-Evans-Polanyi relationship obtained by Boreskov [46]. However, it must be added that significant ambiguity exists for exchange on ceria with reported activation energies in the 67-131 kJ/mol range [29,[50][51][52]. In the case of V 2 O 5 the heat of chemisorption is assumed equal to the desorption activation energy from Dziembaj [53], but this value must also be regarded with some caution, as there is significant ambiguity in the literature concerning the heat of oxygen chemisorption on V 2 O 5 with reported values covering the wide range of 40-250 kJ/mol [24,28,53,54].…”

Section: Sources For the Heat Of Oxygen Chemisorptionmentioning

confidence: 99%

Importance of the oxygen bond strength for catalytic activity in soot oxidation

Christensen

Grunwaldt

Jensen

2016

Applied Catalysis B: Environmental

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The oxygen bond strength on a catalyst, as measured by the heat of oxygen chemisorption, is observed to be a very important parameter for the activity of the catalyst in soot oxidation. With both intimate contact between soot and catalyst (tight contact) and with the solids stirred loosely together (loose contact) the rate constants for a number of catalytic materials outline a volcano curve when plotted against their heats of oxygen chemisorption. However, the optima of the volcanoes correspond to different heats of chemisorption for the two contact situations. In both cases the activation energies for soot oxidation follow linear Brønsted-Evans-Polanyi relationships with the heat of oxygen chemisorption. Among the tested metal or metal oxide catalysts Co 3 O 4 and CeO 2 were nearest to the optimal bond strength in tight contact oxidation, while Cr 2 O 3 was nearest to the optimum in loose contact oxidation. The optimum of the volcano curve in loose contact is estimated to occur between the bond strengths of α-Fe 2 O 3 and α-Cr 2 O 3 . Guided by an interpolation principle Fe a Cr b O x binary oxides were tested, and the activity of these oxides was observed to pass through an optimum for an FeCr 2 O x binary oxide catalyst, which exhibited a rate constant at 550 °C that was 2.3 times higher than the one for pure α-Cr 2 O 3 and 29 times higher than the one for pure α-Fe 2 O 3 .

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Mobility of oxygen and catalytic properties of rare earth oxides with respect to oxidation of hydrogen

Cited by 23 publications

References 0 publications

The influence of lattice oxygen on the initial growth behavior of heteroepitaxial Ge layers on single crystalline PrO2(111)∕Si(111) support systems

The influence of lattice oxygen on the initial growth behavior of heteroepitaxial Ge layers on single crystalline PrO2(111)∕Si(111) support systems

Photoemission study of praseodymia in its highest oxidation state: The necessity of in situ plasma treatment

Importance of the oxygen bond strength for catalytic activity in soot oxidation

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