Rh/CeO2-ZrO2 mixed oxides show improved redox properties compared to Rh/CeO2 due to a low-temperature reduction in the bulk. In the present work we have investigated the Zr-O and Ce-O local structure in Rh/Ce0.5Zr0.5O2 by means of EXAFS and Raman spectroscopy. By introducing Zr4+ into the CeO2 lattice, the oxygen sublattice is strongly modified compared to the ideal fluorite structure of CeO2: the Ce4+ ions retain their coordination while the number of oxygens around the Zr4+ decreases from 8 to 6 due to a displacement of two oxygens to a nonbonding distance. It is suggested that this distortion of the oxygen sublattice generates some mobile oxygens in Rh/Ce0.5Zr0.5O2 which are responsible for the improved redox properties.



Titolo: Relationship between the zirconia-promoted reduction in the Rh-loaded Ce0.5Zr0.5O2 mixed oxide and the Zr-O local structure
Autori: 
VLAIC, GILBERTO
FORNASIERO, Paolo
GEREMIA, SILVANO
KASPAR, JAN
GRAZIANI, MAURO
Data di pubblicazione: 1997
Rivista: 
JOURNAL OF CATALYSIS  
Abstract: Rh/CeO2-ZrO2 mixed oxides show improved redox properties compared to Rh/CeO2 due to a low-temperature reduction in the bulk. In the present work we have investigated the Zr-O and Ce-O local structure in Rh/Ce0.5Zr0.5O2 by means of EXAFS and Raman spectroscopy. By introducing Zr4+ into the CeO2 lattice, the oxygen sublattice is strongly modified compared to the ideal fluorite structure of CeO2: the Ce4+ ions retain their coordination while the number of oxygens around the Zr4+ decreases from 8 to 6 due to a displacement of two oxygens to a nonbonding distance. It is suggested that this distortion of the oxygen sublattice generates some mobile oxygens in Rh/Ce0.5Zr0.5O2 which are responsible for the improved redox properties.
Handle: http://hdl.handle.net/11368/1695065
Digital Object Identifier (DOI): 10.1006/jcat.1997.1644
Appare nelle tipologie:1.1 Articolo in Rivista

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