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High catalytic activity of Au/CeOx/TiO2(110) controlled by the nature of the mixed-metal oxide at the nanometer level

Authors:
Park, J. B.
Graciani, J.
Evans, J.
Stacchiola, D.
Ma, S. G.
Liu, P.
Nambu, A.
Sanz, J. F.
Hrbek, J.
Rodriguez, J. A.
Published by: Proceedings of the National Academy of Sciences of the United States of America
Date: 0 2009
Volume, Number, Pages: 106 13 4975-4980

Accession Number: WOS:000264790600006

Abstract:

Mixed-metal oxides play a very important role in many areas of chemistry, physics, materials science, and geochemistry. Recently, there has been a strong interest in understanding phenomena associated with the deposition of oxide nanoparticles on the surface of a second (host) oxide. Here, scanning tunneling microscopy, photoemission, and density-functional calculations are used to study the behavior of ceria nanoparticles deposited on a TiO2(110) surface. The titania substrate imposes nontypical coordination modes on the ceria nanoparticles. In the CeOx/TiO2(110) systems, the Ce cations adopt an structural geometry and an oxidation state l that are quite different from those seen in bulk ceria or for ceria nanoparticles deposited on metal substrates. The increase in the stability of the Ce3+ oxidation state leads to an enhancement in the chemical and catalytic activity of the ceria nanoparticles. The codeposition of ceria and gold nanoparticles on a TiO2(110) substrate generates catalysts with an extremely high activity for the production of hydrogen through the water-gas shift reaction (H2O + CO -> H-2 + CO2) or for the oxidation of carbon monoxide (2CO + O-2 -> 2CO(2)). The enhanced stability of the Ce3+ state is an example of structural promotion in catalysis described here on the atomic level. The exploration of mixed-metal oxides at the nanometer level may open avenues for optimizing catalysts through stabilization of unconventional surface structures with special chemical activity.