Structure of vanadium oxide supported on ceria by multi-wavelength Raman spectroscopy

Journal Article · Sat Jan 01 04:00:00 EST 2011 · Journal of Physical Chemistry C

DOI:https://doi.org/10.1021/jp2084605· OSTI ID:1042849

Wu, Zili ^[1]

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1. ORNL

ABSTRACT The structure of vanadium oxide species supported on ceria (VOx/CeO2) was investigated under various conditions by in situ multi-wavelength Raman spectroscopy, IR spectroscopy, isotopic labeling and temperature programmed reduction (TPR). For the first time, the detailed structure of dehydrated VOx species was revealed on the polycrystalline ceria support. VOx species can co-exist on ceria surface in the structure of monomer, dimer, trimer, polymer, crystalline V2O5 and CeVO4 as a function of VOx loading. These species interact strongly with both the defect sites and labile surface oxygen of ceria, passivating the redox property of ceria. Under ambient condition, the dispersed VOx species are hydrated into polyvanadate species which can be reversibly dehydrated back to the original structure forms. The ceria support with defect sites facilitates the interaction between water (H218O) and V16Ox species, leading to very facile isotopic oxygen exchange between the two even at room temperature. During H2 reduction, both the VOx species and the ceria support can be reduced with ceria surface being more reducible. The reducibility of various dispersed VOx species scales with their polymerization degree, i.e., polymer > trimer > dimer > monomer. The reoxidation of reduced VOx species is found to proceed via ceria lattice oxygen instead of the gas phase oxygen where ceria acts as an oxygen buffer. The revealed structure evolution of surface VOx species on ceria under hydrated, dehydrated, reduced, and regenerated conditions provides a basis for understanding the vanadia-ceria catalysis.

• Research Organization: Oak Ridge National Laboratory (ORNL); Center for Nanophase Materials Sciences
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1042849
• Journal Information: Journal of Physical Chemistry C, Journal Name: Journal of Physical Chemistry C Journal Issue: 51 Vol. 115; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CATALYSIS
DEFECTS
DIMERS
OXYGEN
POLYMERIZATION
POLYMERS
RAMAN SPECTROSCOPY
SPECTROSCOPY
VANADIUM OXIDES
WATER