Electron Microscopy Studies of Real and Model Oxide Supported Au Catalysts
Yingmin Wang | Download entire thesis

Oxide supported Au catalysts have been the center of intensive research since being
discovered as the most active catalysts for low temperature CO oxidation. However, the
origin of the high activity of these catalysts remains unknown. The complexity of this
catalytic system prevents a clear identification and characterization of the factors truly
affecting its properties. In this thesis research, the attention was focused on certain areas
that are truly crucial for the understanding of the Au catalysts, including the preparation
and activation of Au catalysts, the properties of the TiO2 surface and the interaction
between TiO2 and gold nanoparticles. Electron microscopy was used throughout this re-
search along with other techniques and has been proved to be a powerful and irreplaceable
tool and provide an insight into this catalytic system with a unique angle.

Among all of the findings of this research, the examination of Au catalysts identified
the role of chlorine in accelerating the agglomeration of gold particles and poisoning the
active sites. Studies on the activation of Au/Al2 O3 and Au/TiO2 catalysts demonstrated
the oxidation state and the size of the gold particles were two competing factors during
activation and both were very important. The difference in the mobility of gold species
on oxide surfaces affects them.

The study of the TiO2 surface described the reoxidation process of the TiO2 surface and
a new surface reconstruction, c(2x2), on this surface was reported. Its atomic structure
was solved by applying Direct Methods and Density Functional Theory calculations.
The study of Au/TiO2 model catalysts revealed no preferred orientation between gold
nanoparticles and TiO2 supports with various crystallographic orientations and surface
conditions, and this fact was explained by the influence of surface adsorbates. Model cat-
alyst studies also characterized surface induced sintering, and estimated the temperature
of local heating during surface induced sintering. Finally, the attempt to measure the
catalytic properties of the Au model catalyst was presented and the initial results was
described.