title: High catalytic activity of Au/CeOx/TiO2(110) controlled by the nature of the mixed-metal oxide at the nanometer level.
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 TiO(2)(110) surface. The titania substrate imposes nontypical coordination modes on the ceria nanoparticles. In the CeO(x)/TiO(2)(110) systems, the Ce cations adopt an structural geometry and an oxidation state (+3) 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 Ce(3+) 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 TiO(2)(110) substrate generates catalysts with an extremely high activity for the production of hydrogen through the water-gas shift reaction (H(2)O + CO --> H(2) + CO(2)) or for the oxidation of carbon monoxide (2CO + O(2) --> 2CO(2)). The enhanced stability of the Ce(3+) 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.
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Joon B
authors.initials: JB
authors.lastname: Park
authors.forename: Jesus
authors.initials: J
authors.lastname: Graciani
authors.forename: Jaime
authors.initials: J
authors.lastname: Evans
authors.forename: Dario
authors.initials: D
authors.lastname: Stacchiola
authors.forename: Shuguo
authors.initials: S
authors.lastname: Ma
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Akira
authors.initials: A
authors.lastname: Nambu
authors.forename: Javier Fernández
authors.initials: JF
authors.lastname: Sanz
authors.forename: Jan
authors.initials: J
authors.lastname: Hrbek
authors.forename: José A
authors.initials: JA
authors.lastname: Rodriguez