TY - JOUR
T1 - Physical and chemical properties of Ce1-xZrxO 2 nanoparticles and Ce1-xZrxO2(1 1 1) surfaces
T2 - Synchrotron-based studies
AU - Rodriguez, J. A.
AU - Wang, X.
AU - Liu, G.
AU - Hanson, J. C.
AU - Hrbek, J.
AU - Peden, C. H.F.
AU - Iglesias-Juez, A.
AU - Fernández-García, M.
N1 - Funding Information:
The research carried out at Brookhaven National Laboratory and Pacific Northwest National Laboratory was financed by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences. Work at the “Instituto de Catálisis (CSIC)” was done with financial support from CICYT (project MAT2000-1467). The National Synchrotron Light Source is supported by the Divisions of Materials and Chemical Sciences of DOE. A portion of the work was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility located at Pacific Northwest National Laboratory and supported by the DOE Office of Biological and Environmental Research.
PY - 2005/3/16
Y1 - 2005/3/16
N2 - In this article, we review a series of studies that use synchrotron-based techniques (high-resolution photoemission, time-resolved X-ray diffraction (XRD), and X-ray absorption near-edge spectroscopy) to investigate the physical and chemical properties of Ce1-xZrxO2 nanoparticles and Ce1-xZrxO2(1 1 1) surfaces (x ≤ 0.5). CeO2 and Ce1-xZrxO2 particles in sizes between 4 and 7 nm were synthesized using a novel microemulsion method. The results of XANES (O K-edge, Ce and Zr L III-edges) indicate that the Ce1-xZrxO 2 nanoparticles and Ce1-xZrxO2(1 1 1) surfaces have very similar electronic properties. For these systems, the lattice constant decreased with increasing Zr content, varying from 5.4 Å in CeO2 to 5.3 Å in Ce0.5Zr0.5O 2. Within the fluorite structure, the Zr atoms exhibited structural perturbations that led to different types of Zr-O distances and non-equivalent O atoms in the Ce1-xZrxO2 compounds. The Ce 1-xZrxO2 nanoparticles were more reactive towards H2 and SO2 than the Ce1-xZr xO2(1 1 1) surfaces. The Ce1-xZr xO2(1 1 1) surfaces did not reduce in hydrogen at 300°C. At temperatures above 250°C, the Ce1-xZr xO2 nanoparticles reacted with H2 and water evolved into gas phase. XANES showed the generation of Ce3+ cations without reduction of Zr4+. There was an expansion in the unit cell of the reduced nanoparticles probably as a consequence of a partial Ce 4+ → Ce3+ transformation and the sorption of hydrogen into the bulk of the material. S K-edge XANES spectra pointed to SO4 as the main product of the adsorption of SO2 on the Ce 1-xZrxO2 nanoparticles and Ce 1-xZrxO2(1 1 1) surfaces. Full dissociation of SO2 was seen on the nanoparticles but not on the Ce 1-xZrxO2(1 1 1) surfaces. The metal cations at corner and edge sites of the Ce1-xZrxO2 nanoparticles probably play a very important role in interactions with the H2 and SO2 molecules.
AB - In this article, we review a series of studies that use synchrotron-based techniques (high-resolution photoemission, time-resolved X-ray diffraction (XRD), and X-ray absorption near-edge spectroscopy) to investigate the physical and chemical properties of Ce1-xZrxO2 nanoparticles and Ce1-xZrxO2(1 1 1) surfaces (x ≤ 0.5). CeO2 and Ce1-xZrxO2 particles in sizes between 4 and 7 nm were synthesized using a novel microemulsion method. The results of XANES (O K-edge, Ce and Zr L III-edges) indicate that the Ce1-xZrxO 2 nanoparticles and Ce1-xZrxO2(1 1 1) surfaces have very similar electronic properties. For these systems, the lattice constant decreased with increasing Zr content, varying from 5.4 Å in CeO2 to 5.3 Å in Ce0.5Zr0.5O 2. Within the fluorite structure, the Zr atoms exhibited structural perturbations that led to different types of Zr-O distances and non-equivalent O atoms in the Ce1-xZrxO2 compounds. The Ce 1-xZrxO2 nanoparticles were more reactive towards H2 and SO2 than the Ce1-xZr xO2(1 1 1) surfaces. The Ce1-xZr xO2(1 1 1) surfaces did not reduce in hydrogen at 300°C. At temperatures above 250°C, the Ce1-xZr xO2 nanoparticles reacted with H2 and water evolved into gas phase. XANES showed the generation of Ce3+ cations without reduction of Zr4+. There was an expansion in the unit cell of the reduced nanoparticles probably as a consequence of a partial Ce 4+ → Ce3+ transformation and the sorption of hydrogen into the bulk of the material. S K-edge XANES spectra pointed to SO4 as the main product of the adsorption of SO2 on the Ce 1-xZrxO2 nanoparticles and Ce 1-xZrxO2(1 1 1) surfaces. Full dissociation of SO2 was seen on the nanoparticles but not on the Ce 1-xZrxO2(1 1 1) surfaces. The metal cations at corner and edge sites of the Ce1-xZrxO2 nanoparticles probably play a very important role in interactions with the H2 and SO2 molecules.
KW - High-resolution photoemission
KW - Nanoparticles
KW - Time-resolved X-ray diffraction
UR - http://www.scopus.com/inward/record.url?scp=12844252663&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=12844252663&partnerID=8YFLogxK
U2 - 10.1016/j.molcata.2004.09.069
DO - 10.1016/j.molcata.2004.09.069
M3 - Article
AN - SCOPUS:12844252663
SN - 1381-1169
VL - 228
SP - 11
EP - 19
JO - Journal of Molecular Catalysis A: Chemical
JF - Journal of Molecular Catalysis A: Chemical
IS - 1-2 SPEC. ISS.
ER -