Adsorption of probe molecules to investigate by EPR the redox properties of silver loaded on ceria

Mira Skaf; Sara Hany; Samer Aouad; Madona Labaki; Edmond Abi-Aad; Antoine Aboukaïs

doi:10.1016/j.chemphys.2018.10.015

Adsorption of probe molecules to investigate by EPR the redox properties of silver loaded on ceria

Mira Skaf, Sara Hany, Samer Aouad, Madona Labaki, Edmond Abi-Aad, Antoine Aboukaïs

Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

10% wt Ag/CeO₂ solids were prepared by impregnation (Imp) and deposition-precipitation (DP) and their catalytic activity towards many oxidation reactions were studied in previous works. Three Ag²⁺ signals were identified by electron paramagnetic resonance technique (EPR) only in the (Imp) solid. Further studies of the active sites of 10% Ag/CeO₂ (Imp) and (DP) were conducted in this work. Adsorptions of probe molecules (O₂, CO, CO₂, N₂O, NO, and NO₂) were carried out on the (Imp) and (DP) solids. Adsorption of O₂, CO, CO₂, N₂O, NO results in the formation of O₂ ⁻ species adsorbed on the surface of both (Imp) and (DP) solids according to: O₂ ^-2XO+Ag⁰/CeO₂→Ag⁺/CeO₂+2X (case of (DP) and (Imp)) Or O₂ ^-2XO+Ag⁺/CeO₂→Ag²⁺/CeO₂+2X (case of (Imp) solid) These O₂ ⁻ species were adsorbed on Ce⁴⁺ species with a weak energy of adsorption since the signal of O₂ ⁻ disappeared on the spectra recorded at ambient temperatures. However, some O₂ ⁻ species were more stable than other ones and resisted to heating treatments. The Ag²⁺ species that were reduced due to the vacuum atmosphere used previously to the adsorption were re-oxidized after treatment by nitrogen oxides (N₂O, NO, and NO₂).

Original language	English (US)
Pages (from-to)	131-137
Number of pages	7
Journal	Chemical Physics
Volume	517
DOIs	https://doi.org/10.1016/j.chemphys.2018.10.015
State	Published - Jan 24 2019

Keywords

Adsorption
Ceria
Electron paramagnetic resonance (EPR)
Oxides
Silver

ASJC Scopus subject areas

General Physics and Astronomy
Physical and Theoretical Chemistry

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10.1016/j.chemphys.2018.10.015

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title = "Adsorption of probe molecules to investigate by EPR the redox properties of silver loaded on ceria",

abstract = "10% wt Ag/CeO2 solids were prepared by impregnation (Imp) and deposition-precipitation (DP) and their catalytic activity towards many oxidation reactions were studied in previous works. Three Ag2+ signals were identified by electron paramagnetic resonance technique (EPR) only in the (Imp) solid. Further studies of the active sites of 10% Ag/CeO2 (Imp) and (DP) were conducted in this work. Adsorptions of probe molecules (O2, CO, CO2, N2O, NO, and NO2) were carried out on the (Imp) and (DP) solids. Adsorption of O2, CO, CO2, N2O, NO results in the formation of O2 − species adsorbed on the surface of both (Imp) and (DP) solids according to: O2 -2XO+Ag0/CeO2→Ag+/CeO2+2X (case of (DP) and (Imp)) Or O2 -2XO+Ag+/CeO2→Ag2+/CeO2+2X (case of (Imp) solid) These O2 − species were adsorbed on Ce4+ species with a weak energy of adsorption since the signal of O2 − disappeared on the spectra recorded at ambient temperatures. However, some O2 − species were more stable than other ones and resisted to heating treatments. The Ag2+ species that were reduced due to the vacuum atmosphere used previously to the adsorption were re-oxidized after treatment by nitrogen oxides (N2O, NO, and NO2).",

keywords = "Adsorption, Ceria, Electron paramagnetic resonance (EPR), Oxides, Silver",

author = "Mira Skaf and Sara Hany and Samer Aouad and Madona Labaki and Edmond Abi-Aad and Antoine Abouka{\"i}s",

note = "Publisher Copyright: {\textcopyright} 2018 Elsevier B.V.",

year = "2019",

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doi = "10.1016/j.chemphys.2018.10.015",

language = "English (US)",

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T1 - Adsorption of probe molecules to investigate by EPR the redox properties of silver loaded on ceria

AU - Skaf, Mira

AU - Hany, Sara

AU - Aouad, Samer

AU - Labaki, Madona

AU - Abi-Aad, Edmond

AU - Aboukaïs, Antoine

PY - 2019/1/24

Y1 - 2019/1/24

N2 - 10% wt Ag/CeO2 solids were prepared by impregnation (Imp) and deposition-precipitation (DP) and their catalytic activity towards many oxidation reactions were studied in previous works. Three Ag2+ signals were identified by electron paramagnetic resonance technique (EPR) only in the (Imp) solid. Further studies of the active sites of 10% Ag/CeO2 (Imp) and (DP) were conducted in this work. Adsorptions of probe molecules (O2, CO, CO2, N2O, NO, and NO2) were carried out on the (Imp) and (DP) solids. Adsorption of O2, CO, CO2, N2O, NO results in the formation of O2 − species adsorbed on the surface of both (Imp) and (DP) solids according to: O2 -2XO+Ag0/CeO2→Ag+/CeO2+2X (case of (DP) and (Imp)) Or O2 -2XO+Ag+/CeO2→Ag2+/CeO2+2X (case of (Imp) solid) These O2 − species were adsorbed on Ce4+ species with a weak energy of adsorption since the signal of O2 − disappeared on the spectra recorded at ambient temperatures. However, some O2 − species were more stable than other ones and resisted to heating treatments. The Ag2+ species that were reduced due to the vacuum atmosphere used previously to the adsorption were re-oxidized after treatment by nitrogen oxides (N2O, NO, and NO2).

AB - 10% wt Ag/CeO2 solids were prepared by impregnation (Imp) and deposition-precipitation (DP) and their catalytic activity towards many oxidation reactions were studied in previous works. Three Ag2+ signals were identified by electron paramagnetic resonance technique (EPR) only in the (Imp) solid. Further studies of the active sites of 10% Ag/CeO2 (Imp) and (DP) were conducted in this work. Adsorptions of probe molecules (O2, CO, CO2, N2O, NO, and NO2) were carried out on the (Imp) and (DP) solids. Adsorption of O2, CO, CO2, N2O, NO results in the formation of O2 − species adsorbed on the surface of both (Imp) and (DP) solids according to: O2 -2XO+Ag0/CeO2→Ag+/CeO2+2X (case of (DP) and (Imp)) Or O2 -2XO+Ag+/CeO2→Ag2+/CeO2+2X (case of (Imp) solid) These O2 − species were adsorbed on Ce4+ species with a weak energy of adsorption since the signal of O2 − disappeared on the spectra recorded at ambient temperatures. However, some O2 − species were more stable than other ones and resisted to heating treatments. The Ag2+ species that were reduced due to the vacuum atmosphere used previously to the adsorption were re-oxidized after treatment by nitrogen oxides (N2O, NO, and NO2).

KW - Adsorption

KW - Ceria

KW - Electron paramagnetic resonance (EPR)

KW - Oxides

KW - Silver

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U2 - 10.1016/j.chemphys.2018.10.015

DO - 10.1016/j.chemphys.2018.10.015

M3 - Article

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SN - 0301-0104

VL - 517

SP - 131

EP - 137

JO - Chemical Physics

JF - Chemical Physics

ER -

Adsorption of probe molecules to investigate by EPR the redox properties of silver loaded on ceria

Abstract

Keywords

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