Chemistry Reference
In-Depth Information
sample prepared via the DP approach as compared the sample prepared in UHV.
While more work is certainly necessary to understand the details of the metal-support
interaction in this particular case, this work has demonstrated that progress is being
made in applying surface science methodologies to study Au catalyst preparation
procedures.
5 Synopsis
The growth of Au on ultrathin films and thicker, more bulk-like substrates by
physical vapor deposition has been thoroughly studied and analyzed. The combi-
nation of imaging and spectroscopic techniques has allowed us derive a detailed
picture of how clusters form from single Au atoms to clusters and further on to
nanoparticles. The influence of charge of the particles and their relation to the
adsorption of CO molecules have been discussed. By comparing three case studies,
i.e., MgO, alumina, and iron oxide, the influence of the nature of the support, in
particular, with respect to the charge, has been elucidated. While ultrathin MgO and
alumina lead to electron transfer to the supported Au, iron oxide leads to transfer
from the Au to the support. In order to proceed to more realistic supports we have
modified the magnesia support chemically by hydroxylation and discuss the con-
sequences for Au particle formation, as well as the impact of this modification on
the particle charge. In the case of an iron oxide support it has even been possible to
study Au particle deposition from solution and it is found that if certain conditions
for reduction and calcination are used, the result is rather similar to a preparation of
Au particles from physical vapor deposition. This study also shows that Michael
Mingos comments on the comparability of molecular compounds and surface
adsorbates have been close to the truth.
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