Structure and Reactivity of CoFe2O4(001) Surfaces in Contact with a Thin Water Film

Kox, Tim; Omranpoor, Amir H.; Kenmoe, Stéphane

doi:10.3390/physchem2040023

“…License: CC BY-NC 4.0 experimental studies. Our calculated bulk lattice parameters a = b = 5.753 Å and c = 9.532 Å agree well with the those found experimentally a = b = 5.762 Å and c = 9.439 in Ref [76],. a = b = 5.765…”

supporting

confidence: 91%

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Ndouka ndouka,

Kenmoe,

Mache

et al. 2024

Preprint

0

View full text Add to dashboard Cite

Herein, Mn3O4 spherical particles (SPs) were synthesized by the sol-gel process, followed by thermal annealing at 400 °C. The sample was analyzed by XRD, FTIR, SEM, SBET, XPS, H2-TPR and UV-vis spectroscopy. XRD and FTIR analysis show that Mn3O4 exhibits a tetragonal spinel structure. SEM and SBET analysis display a porous homogeneous surface made of strongly agglomerated spherical-like grains size with an estimated average particle size of ~35 nm, corresponding to a large specific surface area (SBET) of ~81.5 m2/g. XPS analysis indicated that, Mn3O4 were composed of metallic cations (Mn4+, Mn3+, Mn2+) and oxygen species (O2-, OH- and CO32-). The optical energy band gap energy was ~2.55eV. Moreover, Mn3O4 SPs were successfully tested as catalyst with almost 100% conversion of CH4 to CO2 and H2O at a gas hourly space velocity (GHSV) of 72 000 mL3.g-1h-1. The observed performance can be assigned to the cooperated effects of the smallest spherical-like grain size with mesoporous structure as responsible for the larger SBET, and the available surface-active oxygenated species. The cooperative effect of the good reducibility, the higher ratio of active species (OLat/OAds), as well as Density Functional Theory (DFT) calculations suggested that, CH4 total oxidation over the mesoporous Mn3O4 SPs might follow a two-term process in which both Langmuir-Hinshelwood and Mars-van Krevelen mechanisms are cooperatively involved.

show abstract

“…License: CC BY-NC 4.0 experimental studies. Our calculated bulk lattice parameters a = b = 5.753 Å and c = 9.532 Å agree well with the those found experimentally a = b = 5.762 Å and c = 9.439 in Ref [76],. a = b = 5.765…”

supporting

confidence: 91%

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Ndouka ndouka,

Kenmoe,

Mache

et al. 2024

Preprint

0

View full text Add to dashboard Cite

Herein, Mn3O4 spherical particles (SPs) were synthesized by the sol-gel process, followed by thermal annealing at 400 °C. The sample was analyzed by XRD, FTIR, SEM, SBET, XPS, H2-TPR and UV-vis spectroscopy. XRD and FTIR analysis show that Mn3O4 exhibits a tetragonal spinel structure. SEM and SBET analysis display a porous homogeneous surface made of strongly agglomerated spherical-like grains size with an estimated average particle size of ~35 nm, corresponding to a large specific surface area (SBET) of ~81.5 m2/g. XPS analysis indicated that, Mn3O4 were composed of metallic cations (Mn4+, Mn3+, Mn2+) and oxygen species (O2-, OH- and CO32-). The optical energy band gap energy was ~2.55eV. Moreover, Mn3O4 SPs were successfully tested as catalyst with almost 100% conversion of CH4 to CO2 and H2O at a gas hourly space velocity (GHSV) of 72 000 mL3.g-1h-1. The observed performance can be assigned to the cooperated effects of the smallest spherical-like grain size with mesoporous structure as responsible for the larger SBET, and the available surface-active oxygenated species. The cooperative effect of the good reducibility, the higher ratio of active species (OLat/OAds), as well as Density Functional Theory (DFT) calculations suggested that, CH4 total oxidation over the mesoporous Mn3O4 SPs might follow a two-term process in which both Langmuir-Hinshelwood and Mars-van Krevelen mechanisms are cooperatively involved.

show abstract

“…For the sake of better visualization, only water molecules in the contact layer and at the vicinity of the adsorption site are shown. As also observed on many other oxides, ,− the water contact layer is partially dissociated and both H 2 O and OH – species are present. Colors: Co 3+ (pink), Co 2+ (green), O (red), C (brown), and H (white).…”

Section: Computational Detailssupporting

confidence: 61%

Probing the Local Environment of Active Sites during 2-Propanol Oxidation to Acetone on the Co₃O₄ (001) Surface: Insights from First-Principles O K-Edge XANES Spectroscopy

Douma

¹

,

Nono

²

,

Omranpoor

³

et al. 2023

View full text Add to dashboard Cite

We use theoretical X-ray absorption near-edge spectroscopy (XANES) to investigate the electronic structure of the active sites on the Co3O4 (001) surface during 2-propanol oxidation to acetone in humid conditions. In the gas phase, the O K-edge spectra of 2-propanol and acetone, as well that of 2-propoxide considered as a reaction intermediate, present no pre-edge peaks. Upon 2-propanol adsorption at the Co site of the Co3O4 (001) surface, the O K-edge spectrum presents a distinct peak preceded by a bump in the pre-edge region, both due to dipole transitions from O 1s to 2p states hybridized with Co 3d empty states. The formation of 2-propoxide leads to two distinct pre-edge peaks due to the increase of 3d empty states. A further increment of these pre-edge peaks is observed when acetone is formed and is rather ascribed to the new contributions of carbon 2p empty states in the transitions occurring in the pre-edge region. The changes observed in the pre-edge peak along the oxidation were correlated to the electronic configuration and hybridization of the cobalt atom directly bonded to alcohol. The variation of electron densities was also monitored for all surface cobalt atoms including the ones on which molecular water and dissociated water are adsorbed. The PDOS analysis and crystal field theory showed that adsorption of 2-propanol and molecular water on the surface does not change the oxidation state of +3, while surface cobalt atoms bonded to OH groups have an oxidation state of +4. The 3d Löwdin charges analysis shows pronounced cooperative effects between both Co sites during the last oxidation step which corresponds to the decomposition of 2-propoxide to acetone.

show abstract

Structure and Reactivity of CoFe2O4(001) Surfaces in Contact with a Thin Water Film

Cited by 9 publications

References 34 publications

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Probing the Local Environment of Active Sites during 2-Propanol Oxidation to Acetone on the Co₃O₄ (001) Surface: Insights from First-Principles O K-Edge XANES Spectroscopy

Contact Info

Product

Resources

About

Structure and Reactivity of CoFe2O4(001) Surfaces in Contact with a Thin Water Film

Cited by 9 publications

References 34 publications

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Probing the Local Environment of Active Sites during 2-Propanol Oxidation to Acetone on the Co3O4 (001) Surface: Insights from First-Principles O K-Edge XANES Spectroscopy

Contact Info

Product

Resources

About

Probing the Local Environment of Active Sites during 2-Propanol Oxidation to Acetone on the Co₃O₄ (001) Surface: Insights from First-Principles O K-Edge XANES Spectroscopy