Aliovalent doping of CeO<sub>2</sub>: DFT study of oxidation state and vacancy effects

Vanpoucke, Danny E. P.; Bultinck, Patrick; Cottenier, Stefaan; Speybroeck, Véronique Van; Driessche, Isabel Van

doi:10.1039/c4ta02449d

Cited by 97 publications

(65 citation statements)

References 133 publications

(308 reference statements)

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“…At 1023 K current efficiency, up to 100%, was measured towards CO formation 18 . Doping of an aliovalent cation in place of Ce leads to the reduction and formation of oxygen vacancies 19,20,21 . On the introduction of a dopant, oxygen vacancies are formed by both structural and electronic modifications in ceria 22,23 .…”

Section: Introductionmentioning

confidence: 99%

Role of Reduced CeO₂(110) Surface for CO₂ Reduction to CO and Methanol

et al. 2016

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Density functional theory (DFT) calculations were performed to study the mechanism of carbon dioxide (CO 2 ) reduction to carbon monoxide (CO) and methanol (CH 3 OH) on CeO 2 (110) surface. CO 2 dissociates to CO on interacting with the oxygen vacancy on reduced ceria surface.The oxygen atom heals the vacancy site and regenerates the stoichiometric surface via a redox mechanism with intrinsic activation and reaction energies of 259.2 kJ/mole and 238.6 kJ/mole respectively. Lateral interaction of oxygen vacancies were studied by the generation of two oxygen vacancies per unit of CeO 2 surface. Compared to a single isolated vacancy, the activation and reaction energies of CO 2 dissociation on a di-vacancy were approximately reduced to half of its value. Hydrogen atom co-adsorbed on the surface was observed to assist CO 2 dissociation by forming a carboxyl intermediate, CO 2 +H→COOH (∆E act = 39.0 kJ/mole, ∆H = -69.2 kJ/mole) which on subsequent dissociation produces CO via the redox mechanism. On hydrogenation, CO is likely to produce methanol. The energetics of CO hydrogenation to produce methanol showed exothermic steps with activation barriers comparable to the DFT calculations reported for Cu (111) and CeO 2-x /Cu(111) interface. While on the stoichiometric surface, COOH dissociation COOH→CO+OH (∆E act = 55.6 kJ/mole, ∆H =5.7 kJ/mole) is likely to be difficult as compared to rest of the elementary steps, whereas on the reduced surface the energetics of the same step were significantly lowered (∆E act = 47.4 kJ/mole, ∆H = -80.4 kJ/mole). In comparison, hydrogenation of methoxy, H 3 CO+H→H 3 COH, appears to be relatively difficult (∆E act = 58.7 kJ/mole) on the reduced surface.

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Section: Introductionmentioning

confidence: 99%

Role of Reduced CeO₂(110) Surface for CO₂ Reduction to CO and Methanol

et al. 2016

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“…[40][41][42][43][44][45][46][47][48][49] Another trivalent dopant, Ga, enhances the activity of alkyne semi-hydrogenation, 50 69 This U eff was set to 4.5 eV, as it was been previously proven to provide satisfactory results. 55,[70][71][72] Projector-augmented wave (PAW) pseudopotentials 73 were used to describe the core electrons with a plane-wave cutoff energy of 500 eV for the valence electrons (i.e., 5s, 5p, 4f, 6s for Ce atoms, 2s, 2p for O and C atoms, 4s, 4p, 5s, 4d for Zr atoms, 5s, 5p, 6s, 5d for Hf atoms, and 6s, 6p, 5f, 7s for Th atoms).…”

Section: Introductionmentioning

confidence: 99%

Descriptor Analysis in Methanol Conversion on Doped CeO₂(111): Guidelines for Selectivity Tuning

Capdevila‐Cortada

López

2015

ACS Catal.

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ABSTRACT:Descriptors are crucial to systematize and optimize activity, selectivity, and stability of catalysts. Adsorption energies have usually been taken as the main representative parameter that can summarize reaction energies and activation barriers for simple reactions on relatively simple reaction sites. However, more chemically sound terms, which can be directly mapped to experiments, would be more desirable.Besides, larger molecules with more than one potentially active position and complex sites, like the acid-base pairs present in oxides, are typically beyond the scope provided by common linear-scaling methods. In the present work, we have analyzed the selectivity of the conversion of a polyfunctional molecule on a complex oxide that presents both acid-base and redox chemistry. The conversion of methanol to formaldehyde or CO on isovalently doped ceria (111) has been taken as an example.The selectivity towards CO is triggered by the competition between formaldehyde desorption and C-H cleavage. Our results show that, by introducing dopant cations, the activation energy of the first H-stripping of formaldehyde can be decreased so that its conversion becomes favorable over desorption for Zr, Hf doped systems and expanded lattice ceria. More importantly, desorption is controlled by geometric and acid-base factors, whereas C-H cleavage is exclusively electronically governed through acid-base and redox factors. Thus, both geometric and electronic structure parameters are needed to optimize the performance of ceria to attain the desired selectivity. Selectivity is then estimated by a collective descriptor of the surface that incorporates the ensemble size, acid-base, and redox contributions that can be directly compared to experimental values. In addition, this scaling relationship reduces the error associated to more traditional energy-based descriptors. We can anticipate that the present scheme can be extended to metal oxides and other polyfunctionalized catalysts.2

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“…Various oxoiron complexes have been examined, however questions remain about their structure, oxidation state and spin state, and the effect these have on their properties and reactivity . Many of these uncertainties have been clarified through the use of DFAs, where a direct match between spectroscopic features, spin states and structures could be made . One widely discussed example is posed by a fascinating Sc 3+ ‐capped oxoiron complex [(TMC)(Fe III/IV ‐O‐Sc III )(OTf) 4 (OH x )] (TMC = 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane), synthetized by Fukuzumi, Nam and co‐workers and characterized by X‐ray crystallography .…”

Section: Introductionmentioning

confidence: 99%

“…[40,41] Many of these uncertainties have been clarified through the use of DFAs, where a direct match between spectroscopic features, spin states and structures could be made. [6,29,[42][43][44][45][46] One widely discussed example is posed by a fascinating Sc 3+ -capped oxoiron complex [(TMC) (Fe III/IV -O-Sc III )(OTf) 4 (OH x )] (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), synthetized by Fukuzumi, Nam and co-workers and characterized by X-ray crystallography. [47] However, experimentally obtained bond lengths led to doubts about the assignment of the oxidation state of iron.…”

Section: Introductionmentioning

confidence: 99%

Density functional approximations for consistent spin and oxidation states of oxoiron complexes

Vlahović

Gruden

Stepanović

et al. 2019

Int J of Quantum Chemistry

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We report here a computational study on a series of FeII, FeIII, and FeIV hydroxo/oxoiron complexes with a broad palette of ligands. We are interested in assessing the robustness of widely used density functionals for their prediction and description of structures and spin states for the examined oxoiron complexes. We have used a variety of density functional approximations (S12g, LDA, BP86‐D3, OPBE, SSB‐D, B3LYP‐D3, S12h, and MVS), in all cases including solvation and relativistic effects explicitly. One of the main observations of this detailed study is the excellent performance of S12g for both accurate structures and spin state splittings. Moreover, our results show that in general all density functionals can be used as a reliable computational tool for reproducing and predicting geometries, determining the oxidation state of iron, and most are able as well to providing good descriptions of spin state energetics.

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Aliovalent doping of CeO₂: DFT study of oxidation state and vacancy effects

Cited by 97 publications

References 133 publications

Role of Reduced CeO₂(110) Surface for CO₂ Reduction to CO and Methanol

Role of Reduced CeO₂(110) Surface for CO₂ Reduction to CO and Methanol

Descriptor Analysis in Methanol Conversion on Doped CeO₂(111): Guidelines for Selectivity Tuning

Density functional approximations for consistent spin and oxidation states of oxoiron complexes

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Aliovalent doping of CeO2: DFT study of oxidation state and vacancy effects

Cited by 97 publications

References 133 publications

Role of Reduced CeO2(110) Surface for CO2 Reduction to CO and Methanol

Role of Reduced CeO2(110) Surface for CO2 Reduction to CO and Methanol

Descriptor Analysis in Methanol Conversion on Doped CeO2(111): Guidelines for Selectivity Tuning

Density functional approximations for consistent spin and oxidation states of oxoiron complexes

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Aliovalent doping of CeO₂: DFT study of oxidation state and vacancy effects

Role of Reduced CeO₂(110) Surface for CO₂ Reduction to CO and Methanol

Role of Reduced CeO₂(110) Surface for CO₂ Reduction to CO and Methanol

Descriptor Analysis in Methanol Conversion on Doped CeO₂(111): Guidelines for Selectivity Tuning