Growth and Electronic Properties of Ag Nanoparticles on Reduced CeO2-x(111) Films

Ag nanoparticles grown on reduced CeO_2-x thin films have been studied by X-ray photoelec-tron spectroscopy and resonant photoelectron spectroscopy of the valence band to understand the effect of oxygen vacancies in the CeO_2-x thin films on the growth and interfacial elec-tronic properties of Ag. Ag grows as three-dimensional particles on the CeO_2-x(111) surface at 300 K. Compared to the fully oxidized ceria substrate surface, Ag favors the growth of smaller particles with a larger particle density on the reduced ceria substrate surface, which can be attributed to the nucleation of Ag on oxygen vacancies. The binding energy of Ag3d increases when the Ag particle size decreases, which is mainly attributed to the final-state screening. The interfacial interaction between Ag and CeO_2-x(111) is weak. The resonant enhancement of the 4f level of Ce³⁺ species in RPES indicates a partial Ce⁴⁺→Ce³⁺ re-duction after Ag deposited on reduced ceria surface. The sintering temperature of Ag on CeO_1.85(111) surface during annealing is a little higher than that of Ag on CeO₂(111) surface, indicating that Ag nanoparticles are more stable on the reduced ceria surface.     

Oxidation of Reduced Ceria by Incorporation of Hydrogen

The interaction of hydrogen with reduced ceria (CeO_2?x) powders and CeO_2?x(111) thin films was studied using several characterization techniques including TEM, XRD, LEED, XPS, RPES, EELS, ESR, and TDS. The results clearly indicate that both in reduced ceria powders as well as in reduced single crystal ceria films hydrogen may form hydroxyls at the surface and hydride species below the surface. The formation of hydrides is clearly linked to the presence of oxygen vacancies and is accompanied by the transfer of an electron from a Ce³⁺ species to hydrogen, which results in the formation of Ce⁴⁺, and thus in oxidation of ceria.     

A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce20M1Ox (M=Zr,Cr, Mn,Fe, Co,Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide

This work is mainly focused on investigating the effects of different doped metal cations on the formation of Ce₂₀M₁O_x (M=Zr, Cr, Mn, Fe, Co, Sn) composite oxides and their physicochemical and catalytic properties for NO reduction by CO as a model reaction. The obtained samples were characterized by using N₂ physisorption, X‐ray diffraction, laser Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, inductively coupled plasma atomic emission spectroscopy, X‐ray photoelectron spectroscopy, temperature‐programmed reduction by hydrogen and by oxygen (H₂‐TPR and O₂‐TPD), in situ diffuse reflectance infrared Fourier transform spectroscopy, and the NO+CO model reaction. The results imply that the introduction of M^x+ into the lattice of CeO₂ increases the specific surface area and pore volume, especially for variable valence metal cations, and enhances the catalytic performance to a great extent. In this regard, increases in the oxygen vacancies, reduction properties, and chemisorbed O₂^? (and/or O^?) species of these Ce₂₀M₁O_x composite oxides (M refers to variable valence metals) play significant roles in this reaction. Among the samples, Ce₂₀Cr₁O_x exhibited the best catalytic performance, mainly because it has the best reducibility and more chemisorbed oxygen, and significant reasons for these attributes may be closely related to favorable synergistic interactions of the vacancies and near‐surface Ce³⁺ and Cr³⁺. Finally, a possible reaction mechanism was tentatively proposed to understand the reactions.     

Structure of Nano‐sized CeO2 Materials: Combined Scattering and Spectroscopic Investigations

The structure of several nano‐sized ceria, CeO₂, systems was investigated using neutron and X‐ray diffraction and X‐ray absorption spectroscopy. Whilst both diffraction and total pair distribution functions (PDFs) revealed that in all of the samples the occupancy of both Ce⁴⁺ and O^2? are very close to the ideal stoichiometry, the analysis using Reverse Monte Carlo technique revealed significant disorder around oxygen atoms in the nano‐sized ceria samples in comparison to the highly crystalline NIST standard. In addition, the analysis revealed that the main differences observed in the pair correlations from various X‐ray and neutron diffraction techniques were attributable to the particle size of the CeO₂ prepared by the reported three methods. Furthermore, detailed analysis of the Ce L₃‐ and K‐edge EXAFS data support this finding; in particular the decrease in higher shell coordination numbers with respect to the NIST standard, is attributed to differences in particle size.     

Structural and catalytic properties of lanthanide (La, Eu, Gd) doped ceria

Ce_0.9M_0.1O_2−δ mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO₂ (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shift of the F_2g Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce⁴⁺/Ce³⁺. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO₂, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area.     

Interaction of Hydrogen with Ceria: Hydroxylation,Reduction, and Hydride Formation on the Surface and in the Bulk

The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO₂) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO₂(111) thin films and CeO₂ powders, and theoretical calculations of CeO₂(111) surfaces with oxygen vacancies (O_v) at the surface and in the bulk. We show that, on a stoichiometric CeO₂(111) surface, H₂ dissociates and forms surface hydroxyls (OH). On the pre-reduced CeO_2−x samples, both films and powders, hydroxyls and hydrides (Ce−H) are formed on the surface as well as in the bulk, accompanied by the Ce³⁺ ↔ Ce⁴⁺ redox reaction. As the O_v concentration increases, hydroxyl is destabilized and hydride becomes more stable. Surface hydroxyl is more stable than bulk hydroxyl, whereas bulk hydride is more stable than surface hydride. The surface hydride formation is the kinetically favorable process at relatively low temperatures, and the resulting surface hydride may diffuse into the bulk region and be stabilized therein. At higher temperatures, surface hydroxyls can react to produce water and create additional oxygen vacancies, increasing its concentration, which controls the H₂/CeO₂ interaction. The results demonstrate a large diversity of reaction pathways, which have to be taken into account for better understanding of reactivity of ceria-based catalysts in a hydrogen-rich atmosphere.     

Nanosized CeO2–SiO2, CeO2–TiO2, and CeO2–ZrO2 Mixed Oxides: Influence of Supporting Oxide on Thermal Stability and Oxygen Storage Properties of Ceria

The influence of SiO₂, TiO₂, and ZrO₂ on the structural and redox properties of CeO₂ were systematically investigated by various techniques namely, X-ray diffraction (XRD), Raman spectroscopy (RS), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HREM), BET surface area, and thermogravimetry methods. The effect of supporting oxides on the crystal modification of ceria was also mainly focused. The investigated oxides were obtained by soft chemical routes with ultrahigh dilute solutions and were subjected to thermal treatments from 773 to 1073 K. The XRD results suggest that the CeO₂–SiO₂ sample primarily consists of nanocrystalline CeO₂ on the amorphous SiO₂ surface. Both crystalline CeO₂ and TiO₂-anatase phases were noted in the case of CeO₂–TiO₂ sample. Formation of cubic Ce_0.75Zr_0.25O₂ and Ce_0.6Zr_0.4O₂ (at 1073 K) were observed in the case of CeO₂–ZrO₂ sample. The cell ‘a’ parameter estimations revealed an expansion of the ceria lattice in the case of CeO₂–TiO₂, while a contraction is noted in the case of CeO₂–ZrO₂. The DRS studies suggest that the supporting oxides significantly influence the band gap energy of CeO₂. Raman measurements disclose the presence of oxygen vacancies, lattice defects, and displacement of oxide ions from their normal lattice positions in the case of CeO₂–TiO₂ and CeO₂–ZrO₂ samples. The XPS studies revealed the presence of silica, titania, and zirconia in their highest oxidation states, Si(IV), Ti(IV), and Zr(IV) at the surface of the materials. Cerium is present in both Ce⁴⁺ and Ce³⁺ oxidation states. The HREM results reveal well-dispersed CeO₂ nanocrystals over the amorphous SiO₂ matrix in the case of CeO₂–SiO₂, isolated CeO₂ and TiO₂ (A) nanocrystals and some overlapping regions in the case of CeO₂–TiO₂, and nanosized CeO₂ and Ce–Zr oxides in the case of CeO₂–ZrO₂ sample. The exact structural features of these crystals as determined by digital diffraction analysis of HREM experimental images reveal that the CeO₂ is mainly in cubic fluorite geometry. The oxygen storage capacity (OSC) as determined by thermogravimetry reveals that the OSC of mixed oxides is more than that of pure CeO₂ and the CeO₂–ZrO₂ exhibits highest OSC.     

CO2 Reduction by Hydrogen Pre-Reduced Acceptor-Doped Ceria

The reactivity of H₂ pre-reduced acceptor-doped ceria materials Gd_0.10Ce_0.90O_2-δ (GDC10) and Sm_0.15Ce_0.85O_2-δ (SDC15) was tested with respect to the reduction of CO₂ to CO in the context of the reverse water-gas shift reaction. It was demonstrated that not only oxygen vacancies, but also dissolved hydrogen is a reactive species for the reduction of CO₂. Dissolved hydrogen must be considered upon discussion of the mechanism of the reverse water-gas shift reaction on ceria-derived materials apart from oxygen vacancies and formates. The reduction of CO₂ is preceded by the formation of carbonate species of different thermal stability and reactivity. The stability of these carbonates was directly demonstrated by in situ infrared spectroscopy and revealed the largely reversible nature of CO₂ ad- and desorption. In comparison to pre-reduced samples, decreased carbonate coverage is obtained after oxidative treatments of GDC10 and SDC15. No significant effect of the sample treatment (O₂ oxidation or H₂ reduction) on the surface carbonate stability was noticed. Mono-dentate carbonates and carboxylates appear to be more easily formed on pre-reduced (i. e. defective) samples. Ce⁴⁺ reduction to Ce³⁺ (by H₂) and re-oxidation to Ce⁴⁺ (by CO₂) on GDC10/SDC15 were directly monitored by infrared spectroscopic analysis of a distinct, IR-active electronic transition of Ce³⁺. These results show the complex interplay of oxygen vacancy/dissolved hydrogen reactivity and surface chemical aspects in acceptor-doped ceria materials.     

Double‐Oxygen‐Atom Transfer in Reactions of CemO2m+ (m=2–6) with C2H2

Cerium oxide cluster cations (Ce_mO_n⁺, m=2–16; n=2m, 2m±1 and 2m±2) are prepared by laser ablation and reacted with acetylene (C₂H₂) in a fast‐flow reactor. A time‐of‐flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Reactions of stoichiometric Ce_mO_2m⁺ (m=2–6) with C₂H₂ produce Ce_mO_2m?2⁺ clusters, which indicates a “double‐oxygen‐atom transfer” reaction Ce_mO_2m⁺+C₂H₂→Ce_mO_2m?2⁺+(CHO)₂ (ethanedial). A single‐oxygen‐atom transfer reaction channel is also identified as Ce_mO_2m⁺+C₂H₂→Ce_mO_2m?1⁺+C₂H₂O (at least for m=2 and 3). Density functional theory calculations are performed to study reaction mechanisms of Ce₂O₄⁺+C₂H₂, and the calculated results confirm that both the single‐ and double‐oxygen‐atom transfer channels are thermodynamically and kinetically favourable.     

Perylene diimide‐modified magnetic γ‐Fe2O3/CeO2 nanoparticles as peroxidase mimics for highly sensitive colorimetric detection of Vitamin C

Perylene diimide‐modified magnetic γ‐Fe₂O₃/CeO₂ nanoparticles (γ‐Fe₂O₃/CeO₂‐PDI) were prepared and exhibited excellent peroxidase‐like activity. The samples were characterized by HR‐TEM, XRD, Raman, N₂ adsorption, magnetic strength and XPS. The obtained γ‐Fe₂O₃/CeO₂‐PDI had size of 10~20 nm with high specific surface area of 77 m²/g, and could be easily separated from the aqueous solution by using a magnet, which are in favor of its practical application. Due to the decoration of PDI, the γ‐Fe₂O₃/CeO₂‐PDI possessed more surface defects (Ce³⁺) and active oxygen species than that of γ‐Fe₂O₃/CeO₂, resulting in the outstanding catalytic performance. And the composite catalyst also showed highly sensitive and selectivity toward VC with a limit of detection of 0.45 μM. Based on the fluorescent results, a possible hydroxyl radical (?OH) catalytic mechanism was proposed. It is believed that the as‐prepared γ‐Fe₂O₃/CeO₂‐PDI nanoparticles are promising biosensors applied for biomedical and food analysis.     

Understanding the Role of Surface Oxygen in Hg Removal on Un-Doped and Mn/Fe-Doped CeO2(111)

Effects of surface-adsorbed O and lattice O for the CeO₂(111) surface on Hg removal has been researched. In this work, periodic calculations based on density functional theory (DFT) were performed with the on-site Coulomb interaction. Hg is oxidized to HgO via the surface-adsorbed O by overcoming a Gibbs free energy barrier of 114.1 kJ·mol⁻¹ on the CeO₂(111) surface. Mn and Fe doping reduce the activation Gibbs free energy for the Hg oxidation, and energies of 70.7 and 49.6 kJ·mol⁻¹ are needed on Ce_0.96Mn_0.04O₂(111) and Ce_0.96Fe_0.04O₂(111) surfaces. Additionally, lattice O also plays an important role in Hg removal. Hg cannot be oxidized leading to the formation of HgO on the un-doped CeO₂(111) surface owing to the inertness of lattice O, which can be easily oxidized to HgO on Ce_0.96Mn_0.04O₂(111) and Ce_0.96Fe_0.04O₂(111) surfaces. It can be seen that both surface-adsorbed O and lattice O play important roles in removing Hg. The present study will shed light on understanding and developing Hg removal technology on un-doped and Mn/Fe-doped CeO₂(111) catalysts. © 2019 Wiley Periodicals, Inc.     

ESR Study of the Formation of O<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> Radical Anions on Oxidized CeO<Subscript>2</Subscript> and CeO<Subscript>2</Subscript>/ZrO<Subscript>2</Subscript> Adsorbing a CO + O<Subscript>2</Subscript> Mixture

It is demonstrated by ESR measurements that O ₂ ⁻ (CO + O₂) radical anions result from CO + O₂ adsorption on the oxidized surface of CeO₂. These radical anions are stabilized in the coordination sphere of Ce⁴⁺ cations located in isolated and associated anionic vacancies. This reaction shows an activation behavior determined by CO adsorption. The variation of O ₂ ⁻ (CO + O₂) concentration with CO adsorption temperature suggests that surface carbonates and carboxylates participate in this reaction. In the (0.5– 10.0)%CeO₂/ZrO₂ system, O ₂ ⁻ forms on supported CeO₂ and is stabilized on Ce⁴⁺ and Zr⁴⁺ cations. The stability of O ₂ ⁻ -Ce⁴⁺ complexes is lower on supported CeO₂ than on unsupported CeO₂, indicating a strong interaction between the cerium cations and the support.__________Translated from Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 423–429.Original Russian Text Copyright © 2005 by Il’ichev, Kuli-zade, Korchak.     

Synthesis of ceria–zirconia mixed oxide from cerium and zirconium glycolates via sol–gel process and its reduction property

Ceria–zirconia mixed oxide was successfully synthesized via the sol–gel process at ambient temperature, followed by calcination at 500, 700 and 900 °C. The synthesis parameters, such as alkoxide concentration, aging time and heating temperature, were studied to obtain the most uniform and remarkably high‐surface‐area cubic‐phase mixed oxides. The thermal stability of both oxides was enhanced by mutual substitution. Surface areas of the Ce_xZr_1?xO₂ powders were improved by increasing ceria content, and their thermal stability was increased by the incorporation of ZrO₂. The most stable cubic‐phase solid solutions were obtained in the Ce range above 50 mol%. The highest surface area was obtained from the mixed catalyst containing a ceria content of 90 mol% (200 m²/g). Temperature programmed reduction results show that increasing the amount of Zr in the mixed oxides results in a decrease in the reduction temperature, and that the splitting of the support reduction process into two peaks depends on CeO₂ content. The CO oxidation activity of samples was found to be related to its composition. The activity of catalysts for this reaction decreased with a decrease in Zr amount in cubic phase catalysts. Ce₆Zr₄O₂ exhibited the highest activity for CO oxidation. Copyright © 2006 John Wiley & Sons, Ltd.     

Structure and surface properties of ZrO<Subscript>2</Subscript>, CeO<Subscript>2</Subscript>, and Zr<Subscript>0.5</Subscript>Ce<Subscript>0.5</Subscript>O<Subscript>2</Subscript> prepared by a microemulsion method according to X-ray diffraction,TPR, and EPR data

It was established by X-ray diffraction, TPR, and EPR that microemulsion (m.e.) synthesis yields the binary oxides ZrO₂(m.e.) and CeO₂(m.e.) and the mixed oxide Zr_0.5Ce_0.5O₂(m.e.) in the form of a tetragonal, cubic, and pseudocubic phase, respectively, having crystallite sizes of 5–6 nm. The bond energy of surface oxygen in the (m.e.) samples is lower than in their analogues prepared by pyrolysis. Hydrogen oxidation on the oxides under study occurs at higher temperatures than CO oxidation. ZrO₂(m.e.) and CeO₂(m.e.) are active in O₂⁻ formation during NO + O₂ adsorption, while CeO₂ is active during CO + O₂ adsorption, too. However, its amount here is one-half to one-third its amount in the pyrolysis-prepared samples, signifying a reduced number of active sites, which are Zr⁴⁺ and Ce⁴⁺ coordinatively unsaturated cations and Me⁴⁺-O²⁻ pairs. O₂⁻ radical anions are stabilized in the coordination sphere of Zr⁴⁺ coordinatively unsaturated cations via ionic bonding, and in the sphere of Ce⁴⁺ cations, via covalent bonding. Ionic bonds are stronger than ionic-covalent bonds and do not depend on the ZrO₂ phase composition. Zr_0.5Ce_0.5O₂ is inactive in these reactions because of the strong interaction of Zr and Ce cations. It is suggested that Ce^{(4 + β)+} coordinatively unsaturated cations exist on its surface, and their acid strength is lower than that of Zr⁴⁺ and Ce⁴⁺ cations in ZrO₂ and CeO₂, according to the order ZrO₂ > CeO₂ ≥ Zr_0.5Ce_0.5O₂. Neither TPR nor adsorption of probe molecules revealed Zr cations on the surface of the mixed oxide.     

Imaging of Oxygen Diffusion in Individual Platinum/Ce2Zr2Ox Catalyst Particles During Oxygen Storage and Release

The spatial distribution of Ce³⁺ and Ce⁴⁺ in each particle of Ce₂Zr₂O_x in a three‐way conversion catalyst system was successfully imaged during an oxygen storage/release cycle by scanning X‐ray absorption fine structure (XAFS) using hard X‐ray nanobeams. For the first time, nano‐XAFS imaging visualized and identified the modes of non‐uniform oxygen diffusion from the interface of Pt catalyst and Ce₂Zr₂O_x support and the active parts in individual catalyst particles.     

A Mixed Ionic and Electronic Conducting Dual‐Phase Membrane with High Oxygen Permeability

To combine good chemical stability and high oxygen permeability, a mixed ionic‐electronic conducting (MIEC) 75 wt % Ce_0.85Gd_0.1Cu_0.05O_2?δ‐25 wt % La_0.6Ca_0.4FeO_3?δ (CGCO‐LCF) dual‐phase membrane based on a MIEC–MIEC composite has been developed. Copper doping into Ce_0.9Gd_0.1O_2?δ (CGO) oxide enhances both ionic and electronic conductivity, which then leads to a change from ionic conduction to mixed conduction at elevated temperatures. For the first time we demonstrate that an intergranular film with 2–10 nm thickness containing Ce, Ca, Gd, La, and Fe has been formed between the CGCO grains in the CGCO‐LCF one‐pot dual‐phase membrane. A high oxygen permeation flux of 0.70 mL min^?1 cm^?2 is obtained by the CGCO‐LCF one‐pot dual‐phase membrane with 0.5 mm thickness at 950 °C using pure CO₂ as the sweep gas, and the membrane shows excellent stability in the presence of CO₂ even at lower temperatures (800 °C) during long‐term operation.     

Raman, XRD and microscopic investigations on CeO2-Lu2O3 and CeO2-Sc2O3 systems: A sub-solidus phase evolution study

A sub-solidus phase evolution study was done in CeO₂-Sc₂O₃ and CeO₂-Lu₂O₃ systems under slow-cooled conditions from 1400 °C. Long-range order probing of X-ray diffraction technique is utilized in conjunction with the ability of Raman spectroscopy to detect the changes in local co-ordination. Lu₂O₃ showed solubility of 30 mol% in CeO₂, thus forming an anion deficient fluorite-type (F-type) solid solution, whereas Sc₂O₃ did not show any discernible solubility. A biphasic region (F+C) was unequivocally detected by Raman spectroscopy in Ce_1−xLu_xO_2−x/2 (0.4?x?0.9) and in Ce_1−xSc_xO_2−x/2 (0.1?x?0.9) systems. Raman spectroscopy was valuable in studying these systems since oxygen vacancies are created on doping RE₂O₃ into ceria and Raman spectroscopy is very much sensitive to oxygen polarizability and local coordination. Back scattered images collected on representative compositions support the above-mentioned results.     

纳米CexFe1-xO2固溶体的模板法制备及其乙醇水蒸气重整催化性能

以超高比表面炭材料为模板,硝酸盐为氧化物前体,通过改进的模板路线制备了具有较高比表面积的纳米CexFe1-xO2固溶体.采用X射线衍射、拉曼光谱、物理吸附和透射电镜对制备的样品进行了表征.结果表明,α-Fe2O3,CexFe1-xO2固溶体和CeO2的粒子尺寸为5~15nm,CeO2中部分Ce4 离子被Fe3 离子取代,从而形成了CexFe1-xO2固溶体.乙醇水蒸气重整反应结果显示,CexFe1-xO2固溶体比相应的α-Fe2O3和CeO2具有更高的催化活性和对氢气的选择性.     

Water‐Assisted Homolytic Dissociation of Propyne on a Reduced Ceria Surface

The emergence of ceria (CeO₂) as an efficient catalyst for the selective hydrogenation of alkynes has attracted great attention. Intensive research effort has been devoted to understanding the underlying catalytic mechanism, in particular the H₂–CeO₂ interaction. Herein, we show that the adsorption of propyne (C₃H₄) on ceria, another key aspect in the hydrogenation of propyne to propene, strongly depends on the degree of reduction of the ceria surface and hydroxylation of the surface, as well as the presence of water. The dissociation of propyne and the formation of methylacetylide (CH₃CC‐) have been identified through the combination of infrared reflection absorption spectroscopy (IRAS) and DFT calculations. We demonstrate that propyne undergoes heterolytic dissociation on the reduced ceria surface by forming a methylacetylide ion on the oxygen vacancy site and transferring a proton to the nearby oxygen site (OH group), while a water molecule that competes with the chemisorbed methylacetylide at the vacancy site assists the homolytic dissociation pathway by rebounding the methylacetylide to the nearby oxygen site.     

Adsorption and migration growth of the Ce,O, and F adatoms on the CeO2 (111) surface: A density functional theory study

In order to investigate the microscopic behavior of the crystal surface growth of the fluorinated cerium dioxide polishing powder, the adsorption and migration of the Ce, O, and F atoms on the CeO₂ (111) surface were studied by using density functional theory with Hubbard correction +U. The adsorption energies of three single atoms at five high-symmetry sites and the migration activation energies along the migration pathway on the CeO₂ (111) surface were calculated. Results show that the most stable adsorption sites of the Ce, O, and F atoms were the O_h, Ce_bri, and Ce_t sites, respectively. The Ce atom migrated from the O_h to the O_t site. The O atom migrated from the Ce_bri to the O_bri site. The F atom migrated from the Ce_t to the O_h site. The migration activation energies of the Ce, O, and F atoms along the migration pathways were 1.526, 0.597, and 0.263 eV, respectively. The F adatom does not change the spatial configuration of the Ce and the O atoms. When the O vacancy occurs on the CeO₂ (111) surface, the F adatom can make up for the O vacancy defect.