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Crystallography 2018
Structural Chemistry & Crystallography Communication
ISSN: 2470-9905
Page 74
June 04-05, 2018
London, UK
3
rd
Edition of International Conference on
Advanced Spectroscopy,
Crystallography and Applications
in Modern Chemistry
I
n heterogenous catalysis surface structure of metal catalyst
may change what modifies surface interactions that in turn
affect the structure. The process may generate dynamics of
surface that can constitute true origin of chemical activity. One
can consider concept of ‘actve processes’ instead of ‘active sites’.
In our laboratory we have developed in situ powder diffraction
technique that is able to register subtle changes of scattered
intensities due to modifications of the nanocrystal surface and
to interpret these changes via molecular simulations. Our results
allowed quantitative distinction between surface relaxations
and reconstructions [1]. The surface reconstruction in response
to changing atmosphere appears to be quite common for metal
nanocrystals. Sometimes it can lead to cyclic or turbulent
phenomena if the reconstruction triggers change in the adsorbate
coverage that in turn causes re-reconstruction (or cancels it out)
[2]. Gold appears as the metal especially prone to reconstruction.
Our results point to gold surface reconstruction occurring on
adsorption of many reactive gases. Interpreting precisely peak
shape and position we could detect reversible size changes along
given crystallographic direction pointing to reversible changes
of the nanocrystal shape [3]. Gold surface appears to be mobile
enough to quickly increase surface of crystal faces interacting
more favorably with the adsorbate. Monitoring oxidation of CO
we detected also appearance of a new form of nanocrystalline
gold with deep reconstruction of crystal faces leading to a 200
and 220 peak split. The transition may deactivate gold as a
catalyst. Precise monitoring of the metal peak position and shape
during chemical reaction can provide insight into its structure
and dynamics. Degree of the Bragg law violations for various
peaks can indicate difference in the interaction with adsorbate on
various crystall faces.
zkaszkur@ichf.edu.plCRYSTALLOGRAPHY OF DYNAMICS OF METAL NANOCLUSTERS DURING
CHEMICAL REACTION AT THEIR SURFACE
Zbigniew Kaszkur
Institute of Physical Chemistry, Poland
Struct Chem Crystallogr Commun 2018, Volume 4
DOI: 10.21767/2470-9905-C1-006