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Abstract:
A combined approach of grazing incidence X-ray diffraction (GIXRD) and
X-ray reflectivity (XRR) under in operando conditions on polycrystalline
materials is presented. This approach allows tracking of material
changes of amorphous or crystalline nature in the near-surface region.
Crystalline phases formed in operando can be identified by X-ray
diffraction, while by XRR measurements information about the thickness
and the density of overlayers is obtained. The setup also allows
collection of data generated with higher incident angles which permit a
direct comparison of the changes close to the surface and in the bulk of
the materials. Results for the composition In52Pd48 - a mixture of the
intermetallic compounds InPd and In3Pd2 catalyzing the steam reforming
of methanol - in reducing atmosphere and under methanol steam reforming
(MSR) conditions are presented. InPd exhibits a dynamic behavior,
reacting to changes in atmosphere and temperature. The combination of
GIXRD and XRR proves to be a powerful tool to examine model catalysts
under catalytically relevant conditions providing complementary
information to other methods.
