(499f) Multiwalled Carbon Nanotubes Drive the Activity of Metal@Oxide Core-Shell Catalysts in Modular Nanocomposites

Multiwalled Carbon Nanotubes Drive the Activity of Metal@oxide Core-Shell
Catalysts in Modular Nanocomposites

M. Cargnello,^1,2
M. Grzelczak,¹ B. Rodriguez-Gonzalez,³ Z. Syrgiannis,¹
K. Bakhmutsky,⁴

V. La
Parola,⁵ L. M. Liz-Marzán,³ R. J. Gorte,⁴
M. Prato,¹ and P. Fornasiero¹

¹ Department
of Chemical and Pharmaceutical Sciences, ICCOM-CNR, Consortium INSTM,
University of Trieste, via L. Giorgieri 1, 34127 Trieste, Italy

 ² Department of Chemistry,
University of Pennsylvania, 231 S. 34^th Street, Philadelphia, PA
19104, USA

³ Departamento de Química Física, Universidade de Vigo, 36310 Vigo, Spain

⁴ Department of Chemical and Biomolecular
Engineering, University of Pennsylvania, 311A Towne Building, 220 S. 33^rd  Street, Philadelphia, PA 19104, USA

⁵ Istituto per lo Studio dei Materiali Nanostrutturati (ISMN-CNR), Via Ugo
La Malfa 153, Palermo I-90146, Italy

The ability to build hierarchical structures by
arranging different building blocks with nanometer-scale precision is one of
the most useful aspects of nanotechnology. This concept can produce novel
materials with properties that are different from those expected from the
simple sum of the individual blocks. Indeed, the interactions between the
constituent parts in nanometer-scale ensembles can lead to novel electronic,
optical, or catalytic properties not available in the initial building blocks.
In the field of heterogeneous catalysis in particular, the interactions between
the active phase, supports, and promoters is critical for obtaining high
performance materials. These interactions can be both electronic and geometric.
Furthermore, the demands in terms of geometry and binding energy of the active
sites for different catalytic reactions can be very different.

In this
contribution, rational nanostructure manipulation has been used to prepare
nanocomposites in which multiwalled carbon nanotubes (MWCNTs) were embedded
inside mesoporous layers of oxides (TiO2, ZrO2, or CeO2), which in turn contained
dispersed metal nanoparticles (Pd or Pt). We show that the MWCNTs induce the
crystallization of the oxide layer at room temperature and that the mesoporous
oxide shell allows the particles to be accessible for catalytic reactions. In contrast
to samples prepared in the absence of MWCNTs, both the activity and the
stability of core-shell catalysts is largely enhanced, resulting in
nanocomposites with remarkable performance for the water-gas-shift
reaction, photocatalytic reforming of methanol, and Suzuki coupling. The
modular approach shown here demonstrates that high-performance catalytic materials
can be obtained through the precise organization of nanoscale building blocks.