Correlation between the size and the magnetic properties of Ag2+ clusters loaded on ceria surface and their catalytic performance in the total oxidation of propylene. EPR study

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

doi:10.1016/j.chemphys.2018.01.001

Correlation between the size and the magnetic properties of Ag²⁺ clusters loaded on ceria surface and their catalytic performance in the total oxidation of propylene. EPR study

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

Chemistry

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

Abstract

Three different types of Ag²⁺ ions (“a” “b” and “c”) have been identified and examined by electron paramagnetic resonance (EPR) on 10% wt Ag/CeO₂ prepared by impregnation method. One of them, Ag²⁺_(b), behaves differently than the two others, Ag²⁺_(a) and Ag²⁺_(c), under redox atmospheres. The fact that, in reducing conditions (vacuum, propylene, hydrogen, and carbon black), Ag²⁺_(a) and Ag²⁺_(c) species were more easily reduced than Ag²⁺_(b) ones, could not explain the catalytic performance and stability of this latter species compared to the first ones in the reaction of total oxidation of propylene. The EPR technique evidenced that Ag²⁺_(b) species form, upon propene oxidation, a cluster. This cluster is composed of two parallel electron spins (dimer) and three nuclear spins (trimer). It seems that before propylene oxidation, Ag²⁺_(b) clusters were ferromagnetic. This ferromagnetic character of Ag²⁺_(b) species may explain their better catalytic performance, in propylene oxidation, than those of Ag²⁺_(a) and Ag²⁺_(c) ones.

Original language	English (US)
Pages (from-to)	1-5
Number of pages	5
Journal	Chemical Physics
Volume	502
DOIs	https://doi.org/10.1016/j.chemphys.2018.01.001
State	Published - Mar 6 2018

Keywords

Agspecies
Catalytic activity
Dimer
EPR
Redox properties
Trimer

ASJC Scopus subject areas

General Physics and Astronomy
Physical and Theoretical Chemistry

Access to Document

10.1016/j.chemphys.2018.01.001

Cite this

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title = "Correlation between the size and the magnetic properties of Ag2+ clusters loaded on ceria surface and their catalytic performance in the total oxidation of propylene. EPR study",

abstract = "Three different types of Ag2+ ions (“a” “b” and “c”) have been identified and examined by electron paramagnetic resonance (EPR) on 10% wt Ag/CeO2 prepared by impregnation method. One of them, Ag2+(b), behaves differently than the two others, Ag2+(a) and Ag2+(c), under redox atmospheres. The fact that, in reducing conditions (vacuum, propylene, hydrogen, and carbon black), Ag2+(a) and Ag2+(c) species were more easily reduced than Ag2+(b) ones, could not explain the catalytic performance and stability of this latter species compared to the first ones in the reaction of total oxidation of propylene. The EPR technique evidenced that Ag2+(b) species form, upon propene oxidation, a cluster. This cluster is composed of two parallel electron spins (dimer) and three nuclear spins (trimer). It seems that before propylene oxidation, Ag2+(b) clusters were ferromagnetic. This ferromagnetic character of Ag2+(b) species may explain their better catalytic performance, in propylene oxidation, than those of Ag2+(a) and Ag2+(c) ones.",

keywords = "Agspecies, Catalytic activity, Dimer, EPR, Redox properties, Trimer",

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

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AU - Hany, Sara

AU - Skaf, Mira

AU - Aouad, Samer

AU - Gennequin, Cédric

AU - Labaki, Madona

AU - Abi-Aad, Edmond

AU - Aboukaïs, Antoine

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N2 - Three different types of Ag2+ ions (“a” “b” and “c”) have been identified and examined by electron paramagnetic resonance (EPR) on 10% wt Ag/CeO2 prepared by impregnation method. One of them, Ag2+(b), behaves differently than the two others, Ag2+(a) and Ag2+(c), under redox atmospheres. The fact that, in reducing conditions (vacuum, propylene, hydrogen, and carbon black), Ag2+(a) and Ag2+(c) species were more easily reduced than Ag2+(b) ones, could not explain the catalytic performance and stability of this latter species compared to the first ones in the reaction of total oxidation of propylene. The EPR technique evidenced that Ag2+(b) species form, upon propene oxidation, a cluster. This cluster is composed of two parallel electron spins (dimer) and three nuclear spins (trimer). It seems that before propylene oxidation, Ag2+(b) clusters were ferromagnetic. This ferromagnetic character of Ag2+(b) species may explain their better catalytic performance, in propylene oxidation, than those of Ag2+(a) and Ag2+(c) ones.

AB - Three different types of Ag2+ ions (“a” “b” and “c”) have been identified and examined by electron paramagnetic resonance (EPR) on 10% wt Ag/CeO2 prepared by impregnation method. One of them, Ag2+(b), behaves differently than the two others, Ag2+(a) and Ag2+(c), under redox atmospheres. The fact that, in reducing conditions (vacuum, propylene, hydrogen, and carbon black), Ag2+(a) and Ag2+(c) species were more easily reduced than Ag2+(b) ones, could not explain the catalytic performance and stability of this latter species compared to the first ones in the reaction of total oxidation of propylene. The EPR technique evidenced that Ag2+(b) species form, upon propene oxidation, a cluster. This cluster is composed of two parallel electron spins (dimer) and three nuclear spins (trimer). It seems that before propylene oxidation, Ag2+(b) clusters were ferromagnetic. This ferromagnetic character of Ag2+(b) species may explain their better catalytic performance, in propylene oxidation, than those of Ag2+(a) and Ag2+(c) ones.

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