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Powder Diffraction and Surface Spectroscopy


Main focus of our research activities is the crystallographic characterization of inorganic functional materials. The materials are used either as catalysts in chemical reactions or for energy storage and conversion. Structure-property relationships are studied on different length scales from averaged crystal structure to local structures of amorphous or disordered compounds.
 
The research group has a long-lasting experience in the field of in situ diffraction under non-ambient conditions. Different sample environments, which are developed in-house in cooperation with the workshop allow diffraction experiments under non ambient temperatures
(100 K – 1200 K), high gas pressures or different gas atmospheres.

The combination of diffraction methods with surface sensitive methods enables a very comprehensive characterization of solid catalysts. For this purpose, the X-ray photoelectron spectrometer has been equipped with an in situ catalysis cell allowing the analysis of surfaces directly after reaction under different gas atmospheres and variable temperatures.

Main research interests:

    Crystallography of solids: XRD, EM, spectroscopy

    in situ diffraction at non-ambient temperatures, gas pressures and atmospheres

    Microstructure analysis of inorganic catalysts: XRD and TEM

    Total scattering: Pair distribution function studies of disordered or amorphous materials

    Characterization of surfaces by X-ray photoelectron spectroscopy

Claudia Weidenthaler

Priv.-Doz. Dr. Claudia Weidenthaler

April 2017
Guest professorship at the Taishan College, Shandong University / Jinan
April 2016
Guest professorship at the Taishan College, Shandong University / Jinan
2015
Habilitation at the University Duisburg-Essen (Habilitation treatise: Modern Powder Diffraction for Crystallographic Studies of Functional Materials)
2012
Group Leader at the Max-Planck-Institut für Kohlenforschung
since 1999
Senior scientist at the Max-Planck-Institut für Kohlenforschung
1998-1999
Scientist at the Universität Frankfurt
1995-1997
Scientist at the Universität Bremen
1995
Doctoral studies, Universität Mainz (Reinhard X. Fischer)
1984-1991
Study of Geology, Mineralogy and Crystallography, Universität Würzburg
1965
Born in Nittenau / Germany

Untersuchungsmethoden von Materialien unter „non ambient“ Bedingungen, Universität Bochum, WS2010/2011

Informations and documents can be found on the lecture website of Ruhr-Universität Bochum.

since 2013
Expert of the International Energy Agency (IEA) Task 32 "Hydrogen-based energy storage" of the Hydrogen Implementation Agreement
 

Open Position 2017
Further information:

International Year of Crystallography 2014
Summer School: Theory and Practice of Modern Powder Diffraction
Further information:
http://www.kofo.mpg.de/iycr/index.html

SoSe 2017: Universität Duisburg-Essen
Anorganische Chemie IV
VO, 2 SWS, Mi 13 - 15, S05 T05 B01

Research Topics

Powder diffraction experiments under reaction conditions
Powder diffraction experiments under reaction conditions

Powder diffraction experiments under reaction conditions

in situ diffraction experiments are excellent tools to get detailed insight in the behavior of functional materials, such as porous compounds, nanoscaled catalysts or metal hydrides. During a reaction, catalysts may not only pass through structural transformations or changes of the microstructure. Also particle growth or phase segregation may occur. Experiments under elevated temperatures are of high value if sintering effects or phase changes influence catalytic properties significantly. The catalytic decomposition of ammonia has been used as a model reaction to analyze catalysts under reaction conditions. The analysis of molybdenum catalysts under NH3 atmosphere shows the formation of MoNx starting from the metal oxide precursor, structural phase changes and a change of the microstructure. These facts are correlated with changes of the catalytic activity and stability.

Figure above: In situ powder diffraction patterns of Mo-based catalysts (left) and the change of the microstructure (right).

Publications:

Gu, Y.-Q., Fu, X.-P., Du, P.-P., Gu, D., Jin, Z., Huang, Y.-Y., Si, R., Zheng, L.-Q., Song, Q.-S., Jia, C.-J., Weidenthaler, C.*
In Situ X-ray Diffraction Study of Co–Al Nanocomposites as Catalysts for Ammonia Decomposition.
J. Phys. Chem.C. (2015) 119(30), 17102-17110.
doi:10.1002/anie.201501475

Tagliazucca, V.; Schlichte, K.; Schüth, F.; Weidenthaler, C.*
Molybdenum-based catalysts for the decomposition of ammonia: In situ X-ray diffraction studies, microstructure and catalytic properties,
J. Catal. (2013) 305, 277-289.
doi:10.1016/j.jcat.2013.05.011

Tagliazucca, V.; Leoni M.; Weidenthaler, C.*
Crystal structure and microstructural changes of molybdenum nitrides traces during catalytic reaction by in situ X-ray diffraction studies.
Phys.Chem.Chem.Phys. (2014)16, 6182-6188.
doi:10.1039/C3CP54578D

 

Crystallography of energy relevant compounds: complex metal hydrides and molecular aminoalanes
Crystallography of energy relevant compounds: complex metal hydrides and molecular aminoalanes

Crystallography of energy relevant compounds: complex metal hydrides and molecular aminoalanes

Complex metal hydrides are inorganic compounds which are interesting as potential solid-state hydrogen storage materials. On the other hand, molecular aminoalanes consisting of aluminum and nitrogen as backbone elements carry intriguingly high amounts of hydrogen.

The structural characterization of the new hydrogen carrier compounds is in the center of interest. New crystal structures have been solved directly from powder diffraction data (Neutron and X-ray) by simulated annealing methods or by the combination of DFT calculations and simulation studies in collaboration with theoretical chemist.

Dehydrogenation and rehydrogenation of hydrides are monitored by means of in situ X-ray diffraction experiments. For this purpose new sample cells had to been developed especially for in-house instruments to follow hydrogenation experiments also under elevated pressure and non-ambient temperatures.

Figure above: In situ cell for laboratory XRD experiments working at elevated H2 pressures and temperatures (left), used for hydrogenation experiments of LaNi5 (right).

Publications:

Bernert, T., Ley, M. B., Ruiz-Fuertes, J., Fischer, M., Felderhoff, M., Weidenthaler, C.*
Molecular structure of diethylaminoalane in the solid state: an X-ray powder diffraction, DFT calculation and Raman spectroscopy study.
Acta Cryst. B, (2016) 72, 232-240.
doi:10.1107/S2052520616000093

Moury, R., Hauschild, K., Kersten, W., Ternieden, J., Felderhoff, M., Weidenthaler, C*.
An in situ powder diffraction cell for high-pressure hydrogenation experiments using laboratory X-ray diffractometers.
J. Appl. Cryst. (2015) 45(Part 1), 79-84.
10.1107/S1600576714025692

Bernert, T., Krech, D., Kockelmann, W., Felderhoff, M., Frankcombe, T. J., Weidenthaler, C.*
Crystal Structure Relation between Tetragonal and Orthorhombic CsAlD 4 : DFT and Time-of-Flight Neutron Powder Diffraction Studies.
Eur. J. Inorg. Chem., (2015) 33, 5545-5550.
doi:10.1002/ejic.201500841
 

Pair distribution function analysis: investigation of the local structure of amorphous or disordered materials
Pair distribution function analysis: investigation of the local structure of amorphous or disordered materials

Pair distribution function analysis: investigation of the local structure of amorphous or disordered materials

Apart from crystal structure solution or crystal structure refinements, powder diffraction can also be used to analyze the real structure of a compound. Pair Distribution Function analysis, PDF, uses the Fourier transforms of the diffraction pattern, to determine the probability of finding two atoms within a defined distance to each other. With this, the coordination environment of locally ordered structures can be determined. The TEM image shows Au@Pt nanoparticles on a carbon support. Local structure analysis can identify whether the particles are alloys, intermetallic compounds, core shell particles or simply two isolated metal phases (see Figure).

Figure above: Left: TEM image of Au@Pt on carbon, right: measured PDF curve of Au@Pt on C and the simulated curves for Au and Pt. 
 

Instrumental Equipment
Instrumental Equipment

Instrumental Equipment

X-ray photoelectron spectrometer (Kratos HSi) for the chemical analysis of surfaces of solids.
The spectrometer is equipped with a dual anode as well as with a monochromatic Al-source. During the measurements sample can be heated or cooled directly in the analysis chamber.

Stoe STADI P transmission diffractometers
(Mo-radiation)
The diffractometers are equipped with a Mo-source, primary Germanium monochromators and position sensitive detectors (linear PSD, Mythen).
For in situ measurements a STOE high temperature furnace (up to 950°C) and a low temperature sample environment (Oxford cryostat, 100-500K) are available. Specific sample cells allow the measurement under high gas pressures.

 X'Pert PRO diffractometer (PANalytical)
The diffractometer can be used with a primary monochromator for high resolution Bragg Brentano measurements, a hybrid monochromator for capillary measurements, and divergence slit setup for conventional Bragg-Brentano experiments. Data collection is performed with a X’Celerator detector.
For in situ data collection, a reaction chamber from Anton Paar (XRK900) can be attached.

In addition, in the department of Heterogeneous Catalysis the following X-ray instruments are availbale:

Stoe STADI P transmission diffractometer (Cu-radiation)

Stoe STADI P Theta/Theta diffractometer (Cu-radiation)
equipped with a heating chamber (1500°C), sample changer, stage for thin films measurements

Anton Paar SAXSess (small angle scattering)
thermostatically controlled sample stage, flow cell

 

 

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  •  Ulrich Holle

    Holle, Ulrich

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    Onur Sahin, Ezgi

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  •  Seyma Ortatatli

    Ortatatli, Seyma

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  • Dr. Valeria Tagliazucca

    Dr. Tagliazucca, Valeria

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  •  Jan Ternieden

    Ternieden, Jan

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  •  Jo-Chi Tseng

    Tseng, Jo-Chi

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  • Priv.-Doz. Dr. Claudia Weidenthaler

    Priv.-Doz. Dr. Weidenthaler, Claudia

    +49(0)208/306-2181

    claudia.weidenthaler((atsign))mpi-mail.mpg.de

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