TY - JOUR
T1 - 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
AU - Hany, Sara
AU - Skaf, Mira
AU - Aouad, Samer
AU - Gennequin, Cédric
AU - Labaki, Madona
AU - Abi-Aad, Edmond
AU - Aboukaïs, Antoine
N1 - Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/3/6
Y1 - 2018/3/6
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.
KW - Agspecies
KW - Catalytic activity
KW - Dimer
KW - EPR
KW - Redox properties
KW - Trimer
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U2 - 10.1016/j.chemphys.2018.01.001
DO - 10.1016/j.chemphys.2018.01.001
M3 - Article
AN - SCOPUS:85040328727
SN - 0301-0104
VL - 502
SP - 1
EP - 5
JO - Chemical Physics
JF - Chemical Physics
ER -