Au/CeOx/TiO2(110)

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


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 (+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 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+CO3H2+CO2) or for the oxidation of carbon
monoxide (2CO + O2 3 2CO2). 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.

Park J et al, PNAS March 31, 2009 vol. 106 no. 13, 4975–4980