First-principles study of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Pt</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Ce</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mn>111</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math>interface

Yang, Zhou; Lu, Zhansheng; Luo, Gaixia

doi:10.1103/physrevb.76.075421

Cited by 84 publications

(36 citation statements)

References 43 publications

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“…Fabris et al 37 and Hermansson et al 38 predicted with DFT that Cu binds more strongly to stoichiometric sites than to oxygen vacancies on CeO 2 (111) terraces, by 1.4 and 1.2 eV (135 and 116 kJ/mol), respectively; whereas Pacchioni et al 39 predicted with DFT that Ag binds more weakly to stoichiometric sites than to oxygen vacancies on CeO 2 (111) terraces. Similarly, DFT indicates that Au, 40−42 Pt, 43 and Pd 44 bind more weakly to stoichiometric sites than to oxygen vacancies on CeO 2 (111) terraces.…”

Section: Discussionmentioning

confidence: 95%

Energetics of Cu Adsorption and Adhesion onto Reduced CeO₂(111) Surfaces by Calorimetry

et al. 2015

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The morphology and interfacial energetics of vapor-deposited Cu on slightly reduced CeO 2 (111) surfaces at 300 K have been studied using single crystal adsorption calorimetry (SCAC), He + low-energy ion scattering spectroscopy (ISS), Xray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). Copper grows as three-dimensional nanoparticles with a density of ∼10 13 particles/cm 2 on CeO 2−x (111) (x = 0.05, 0.1, and 0.2). The initial heat of adsorption of Cu decreased with the extent of reduction, showing that stoichiometric ceria adsorbs Cu more strongly than oxygen vacancies. On CeO 1.95 (111), the heat dropped quickly with coverage in the first 0.1 ML, attributed to nucleation of Cu clusters on stoichiometric steps, followed by the Cu particles spreading onto less favorable sites (step vacancies and terraces). Above ∼0.1 ML (>0.8 nm in diameter), the Cu adsorption energies showed no variation with extent of ceria reduction: the heat of adsorption increased slowly with coverage (particle size) due to the formation of more Cu−Cu bonds per adatom as the size grows, finally approaching the heat of sublimation of bulk Cu by 3.5 ML (2.5 nm). The adhesion energy of Cu(solid) to CeO 1.95 (111) was found to be 3.52 J/m 2 for 2.2 nm diameter particles, decreasing slightly with the extent of reduction. The Ce 3d XPS line shape showed an increase in the Ce 3+ /Ce 4+ ratio with Cu coverage, corresponding to donation of at most ∼0.17 and 0.06 electrons per Cu atom to CeO 1.95 (111) and CeO 1.8 (111), respectively. INTRODUCTIONHeterogeneous catalysts are generally composed of late transition metal nanoparticles dispersed over high surface area oxide supports. The interaction of the supported metal and underlying oxide can greatly influence catalytic properties such as long-term sinter resistance, activity, and selectivity. To improve our understanding of how the choice of metal and support can influence catalytic properties, detailed studies of model systems, where metal atoms are vapor deposited onto single crystal oxide supports, are often employed. With these model systems, the structure of the support surface, the size of the metal particles, and surface cleanliness can be better controlled. 1−5 Studies of this type provide the basic understanding necessary for the intelligent design of new, more efficient, and greener catalysts. Here we apply that approach to study model Cu/CeO 2 catalysts consisting of Cu nanoparticles grown by vapor deposition on CeO 2 (111) surfaces with controlled extents of reduction.We study the energies of the Cu atoms in this system using single crystal adsorption calorimetry (SCAC). This method directly measures the adsorption energy of the incoming metal atoms as they bind to the oxide surface, and to metal nanoparticles on that surface as they grow in size. 6−11 The Cu nanoparticle morphology is characterized using ion scattering spectroscopy (ISS) and X-ray photoelectron spectroscopy (XPS). Adsorption energies measured using SCAC along with detailed adsorbate structura...

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Section: Discussionmentioning

confidence: 95%

Energetics of Cu Adsorption and Adhesion onto Reduced CeO₂(111) Surfaces by Calorimetry

et al. 2015

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“…Density functional theory (DFT) studies on the adsorption of Pt atoms on CeO 2 , for example, suggest that charge redistribution from Pt to neighboring Ce 4 + centers may occur, thus reducing the oxidation state of the cation. [44] In view of these considerations, we may tentatively suggest that the slight initial reduction observed upon Pt deposition at 300 K may be due to such a charge-transfer effect at the Pt/ CeO 2 interface, whereas the more pronounced reduction after annealing to 500 K may be due to oxygen reverse spillover from CeO 2 to the Pt nanoparticles. This suggestion would be in accord within the temperature range previously reported for oxygen activation and reverse spillover on Rh/CeO 2 [28] or Pd/ ceria-zirconia.…”

Section: Morphology and Thermal Behavior Of Pt/ceo 2 /Cu(111)mentioning

confidence: 93%

Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

et al. 2010

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Ceria-based supported noble-metal catalysts release oxygen, which may help to reduce the formation of carbonaceous residues, for example during hydrocarbon reforming. To gain insight into the microscopic origins of these effects, a model study is performed under ultrahigh-vacuum conditions using single-crystal-based supported model catalysts. The model systems are based on ordered CeO(2)(111) films on Cu(111), on which Pt nanoparticles are grown by physical vapor deposition. The growth and structure of the surfaces are characterized by means of scanning tunneling microscopy, and the electronic structure and reactivity are probed by X-ray photoelectron spectroscopy. Specifically, it is shown that the fully oxidized CeO(2) thin films undergo slight reduction upon Pt deposition (CeO(1.99)). This effect is enhanced upon annealing (CeO(1.96)), thus indicating facile oxygen release and reverse spillover. The model system is structurally stable up to temperatures exceeding 700 K. The activation of methane is investigated using high-kinetic-energy CH(4) (0.83 eV), generated by a supersonic molecular beam. It is shown that dehydrogenation occurs under rapid formation of CH or C species without detectable amounts of CH(3) being formed, even at low temperatures (100 K). The released hydrogen spills over to the CeO(2) support, which leads to the formation of OH groups. At 200 K and above, the OH groups start to decompose leaving additional Ce(3+) centers behind (CeO(1.97-1.94)). At up to 700 K, carbon deposits are quantitatively removed by reaction with oxygen, which is supplied by reverse spillover from the CeO(2) film, thus leading to substantial reduction of the support (approximately CeO(1.90-1.85)).

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“…This work has shown that metal dopants can enhance the oxygen vacancy formation energy and reactivity of ceria. In parallel, there have been a number of modelling studies of metal doping of ceria bulk and surfaces, which also show a smaller oxygen vacancy formation energy upon doping 11,12,[34][35][36][37][38][39][40][41][42][43][44] . oxygen hole are present and (iv) La doping of both surfaces makes them more reactive to CO oxidation compared to the undoped surfaces.…”

Section: Introductionmentioning

confidence: 99%

Charge Compensation and Ce³⁺Formation in Trivalent Doping of the CeO₂(110) Surface: The Key Role of Dopant Ionic Radius

Nolan

2011

J. Phys. Chem. C

101

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In this paper, we use density functional theory corrected for on-site Coulomb interactions (DFT + U) and hybrid DFT (HSE06 functional) to study the defects formed when the ceria (110) surface is doped with a series of trivalent dopants, namely, Al3+, Sc3+, Y3+, and In3+. Using the hybrid DFT HSE06 exchange-correlation functional as a benchmark, we show that doping the (110) surface with a single trivalent ion leads to formation of a localized MCe / + OO • (M = the 3+ dopant), O− hole state, confirming the description found with DFT + U. We use DFT + U to investigate the energetics of dopant compensation through formation of the 2MCe ′ +VO ·· defect, that is, compensation of two dopants with an oxygen vacancy. In conjunction with earlier work on La-doped CeO2, we find that the stability of the compensating anion vacancy depends on the dopant ionic radius. For Al3+, which has the smallest ionic radius, and Sc3+ and In3+, with intermediate ionic radii, formation of a compensating oxygen vacancy is stable. On the other hand, the Y3+ dopant, with an ionic radius close to that of Ce4+, shows a positive anion vacancy formation energy, as does La3+, which is larger than Ce4+ (J. Phys.: Condens. Matter201020135004). When considering the resulting electronic structure, in Al3+ doping, oxygen hole compensation is found. However, Sc3+, In3+, and Y3+ show the formation of a reduced Ce3+ cation and an uncompensated oxygen hole, similar to La3+. These results suggest that the ionic radius of trivalent dopants strongly influences the final defect formed when doping ceria with 3+ cations. In light of these findings, experimental investigations of these systems will be welcome.

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First-principles study of thePt∕CeO2(111)interface

Cited by 84 publications

References 43 publications

Energetics of Cu Adsorption and Adhesion onto Reduced CeO₂(111) Surfaces by Calorimetry

Energetics of Cu Adsorption and Adhesion onto Reduced CeO₂(111) Surfaces by Calorimetry

Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

Charge Compensation and Ce³⁺Formation in Trivalent Doping of the CeO₂(110) Surface: The Key Role of Dopant Ionic Radius

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First-principles study of thePt∕CeO2(111)interface

Cited by 84 publications

References 43 publications

Energetics of Cu Adsorption and Adhesion onto Reduced CeO2(111) Surfaces by Calorimetry

Energetics of Cu Adsorption and Adhesion onto Reduced CeO2(111) Surfaces by Calorimetry

Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

Charge Compensation and Ce3+Formation in Trivalent Doping of the CeO2(110) Surface: The Key Role of Dopant Ionic Radius

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Energetics of Cu Adsorption and Adhesion onto Reduced CeO₂(111) Surfaces by Calorimetry

Energetics of Cu Adsorption and Adhesion onto Reduced CeO₂(111) Surfaces by Calorimetry

Charge Compensation and Ce³⁺Formation in Trivalent Doping of the CeO₂(110) Surface: The Key Role of Dopant Ionic Radius