Influence of the Arrangement of the Octahedrally Coordinated Trivalent Cobalt Cations on the Electrical Charge Transport and Surface Reactivity

Ngamou, Patrick Hervé Tchoua; Bahlawane, Naoufal

doi:10.1021/cm1004642

Cited by 74 publications

(29 citation statements)

References 41 publications

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“…The gaps at 1.55 and 2.19 eV are direct allowed transitions. These transitions are assigned to a charge transfer O 2− ➔Co 3+ (the former) and a transition O 2− ➔Co 2+ (the latter) [45][46][47][48][49]. The corresponding spectrum of Co 3 O 4 -P-NS in Figure 2 3 Journal of Nanomaterials [50,51]; this is in accordance with the smaller crystallite size observed in the PXRD analysis.…”

Section: Light Irradiation Of Co 2 Bubbled In Water In the Presence Osupporting

confidence: 75%

Production of Methanol from Aqueous CO₂ by Using Co₃O₄ Nanostructures as Photocatalysts

Pocoví‐Martínez

Zumeta-Dubé

Díaz

2019

Journal of Nanomaterials

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In this work, we report for the first time the photocatalytic activity of Co3O4 nanostructures for the reduction of aqueous CO2 to methanol (MeOH). This could be considered a simple example of artificial photosynthesis. The photocatalysis experiments were developed under simulated solar light of 100 mW/cm2 and without using any sacrificial agent. To carry out this study, nanostructured mixed valence cobalt oxide (Co3O4) powders, with porous nanoparticle aggregates of different morphologies, have been prepared by two synthesis methods. The characterization of structural (PXRD, XPS, SEM, and TEM) and optical (UV-vis-NIR, Raman, and FT-IR) properties, magnetization curves, and surface area (BET) was accomplished.

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Section: Light Irradiation Of Co 2 Bubbled In Water In the Presence Osupporting

confidence: 75%

Production of Methanol from Aqueous CO₂ by Using Co₃O₄ Nanostructures as Photocatalysts

Pocoví‐Martínez

Zumeta-Dubé

Díaz

2019

Journal of Nanomaterials

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“…42 Regarding the band structure, a debate is still opened with the band gap width of Co 3 O 4 at the Fermi level. Most of the results reported in the literature, based on optical measurements mainly, usually describe two band gaps of C1.6 eV and C2-2.5 eV, [43][44][45][46] while some references also reported a band gap with a lower value of C0.8 eV, 5,6,19 and thus claim that Co 3 O 4 would not be a highly correlated electron material in contrast to the Mott insulator CoO. The last hypothesis would be described within the GGA+U formalism by using a lower value of U eff for the d electrons, especially for the Co III B ions.…”

Section: Co 3 Omentioning

confidence: 99%

First-principles electronic structure calculations for the whole spinel oxide solid solution range Mn_xCo_3−xO₄ (0 ≤ x ≤ 3) and their comparison with experimental data

Arras

Guillemet‐Fritsch

et al. 2016

Phys. Chem. Chem. Phys.

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Transition metal spinel oxides have recently been suggested for the creation of efficient photovoltaic cells or photocatalysts. These compounds can be easily tuned by doping to adapt their electronic or magnetic properties. However, their cation distribution is very complex and band structures are still a subject of controversy. We propose a complete density functional theory investigation of MnCoO compounds, using different approximations in order to explain the variation of these properties as a function of composition (for 0 ≤ x ≤ 3) and determine the electronic structure over the whole solid solution range. A detailed study of their atomic structure, magnetic properties and electronic structure is given and compared with experimental data. The unit cell volume calculated for each composition is in agreement with the volume obtained experimentally in ceramics, while a cubic-to-tetragonal structural transition is predicted at x = 2.0. An antiferromagnetic to ferrimagnetic behavior is observed at the lowest ordering temperature depending on the composition. The band gap, deduced from our band structure calculations, strongly decreases upon doping of the end members CoO and MnO, but is partly restored by the tetragonal distortion. A direct band gap, close to 0.5-0.8 eV, is calculated for 0.25 ≤ x ≤ 2.25, justified by inter-metal transitions from Mn ions on octahedral sites.

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“…The mechanism of conductivity of perovskite type oxides is strongly correlated to the overlap of the O 2p and Fe 3d orbitals. 66 The extent of overlap of the O 2p and Fe 3d orbitals is characterised by the Fe-O bond distance (B-O) as detailed in Table 2 16,30 In addition, the Y Fe substituted material exhibited a lower conductivity compared to La Ba .…”

Section: Electronic Conductivitymentioning

confidence: 99%

A DFT+U study of A-site and B-site substitution in BaFeO_3−δ

Baiyee

Chen

Ciucci

2015

Phys. Chem. Chem. Phys.

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BaFeO3-δ (BFO)-based perovskites have emerged as cheap and effective oxygen electrocatalysts for oxygen reduction reaction at high temperatures. The BFO cubic phase facilitates a high oxygen deficiency and is commonly stabilised by partial substitution. Understanding the electronic mechanisms of substitution and oxygen deficiency is key to rational material design, and can be realised through DFT analysis. In this work an in-depth first principle DFT+U study is undertaken to determine site distinctive characteristics for 12.5%, Y, La and Ce substitutions in BFO. In particular, it is shown that B-site doped structures exhibit a lower energy cost for oxygen vacancy formation relative to A site doping and pristine BFO. This is attributed to the stabilisation of holes in the oxygen sub-lattice and increased covalency of the Fe-O bonds of the FeO6 octahedra in B-site-substituted BFO. Charge analysis shows that A-site substitution amounts to donor doping and consequently impedes the accommodation of other donors (i.e. oxygen vacancies). However, A-site substitution may also exhibit a higher electronic conductivity due to less lattice distortion for oxygen deficiency compared to B-site doped structures. Furthermore, analysis of the local structural effects provides physical insight into stoichiometric expansions observed for this material.

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Influence of the Arrangement of the Octahedrally Coordinated Trivalent Cobalt Cations on the Electrical Charge Transport and Surface Reactivity

Cited by 74 publications

References 41 publications

Production of Methanol from Aqueous CO₂ by Using Co₃O₄ Nanostructures as Photocatalysts

Production of Methanol from Aqueous CO₂ by Using Co₃O₄ Nanostructures as Photocatalysts

First-principles electronic structure calculations for the whole spinel oxide solid solution range Mn_xCo_3−xO₄ (0 ≤ x ≤ 3) and their comparison with experimental data

A DFT+U study of A-site and B-site substitution in BaFeO_3−δ

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Influence of the Arrangement of the Octahedrally Coordinated Trivalent Cobalt Cations on the Electrical Charge Transport and Surface Reactivity

Cited by 74 publications

References 41 publications

Production of Methanol from Aqueous CO2 by Using Co3O4 Nanostructures as Photocatalysts

Production of Methanol from Aqueous CO2 by Using Co3O4 Nanostructures as Photocatalysts

First-principles electronic structure calculations for the whole spinel oxide solid solution range MnxCo3−xO4 (0 ≤ x ≤ 3) and their comparison with experimental data

A DFT+U study of A-site and B-site substitution in BaFeO3−δ

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Production of Methanol from Aqueous CO₂ by Using Co₃O₄ Nanostructures as Photocatalysts

Production of Methanol from Aqueous CO₂ by Using Co₃O₄ Nanostructures as Photocatalysts

First-principles electronic structure calculations for the whole spinel oxide solid solution range Mn_xCo_3−xO₄ (0 ≤ x ≤ 3) and their comparison with experimental data

A DFT+U study of A-site and B-site substitution in BaFeO_3−δ