Electron microscopy group

Milivoj Plodinec, Hannah C. Nerl, Frank Girgsdies, Robert Schlögl, Thomas Lunkenbein
This operando TEM study shows the two faces of chemical dynamics, its dependence on the change in local chemical potential and its impact on catalysis on the behavior of Pt nanoparticles during CO oxidation. We found that during the catalytic light-off, in which the changes in gas composition locally dominate, the irreversible transformation prevails. This leads to faceted particles and deactivation later in the process.  From the ignition point on, partial reversible structural dynamics are present, which preserve the activity and occur predominantly at constant chemical potential. more
Luis Sandoval Diaz, Milivoj Plodinec, Danail Ivanov, Stéphane Poitel, Adnan Hammud, Hannah C. Nerl, Robert Schlögl, Thomas Lunkenbein
Using a custom-built tubular reactor for the ESEM, we have investigated the importance of phase transitions during the production of synthesis gas from CO2 and CH4 mixtures. In particular, oxide-metal transition was of great importance for the activity. Activation energies from operando measurement are consistent with fixed bed reactors. Hysteresis in CO production during heating and cooling was found and correlated with surface behavior. more
Jan Folke, Kassiogé Dembélé, Frank Girgsdies, Huiqing Song, Rene Eckert, Stephan Reitmeier, Andreas Reitzmann, Robert Schlögl, Thomas Lunkenbein, Holger Ruland
Ammonia synthesis is considered a key reaction for the energy transition. In this work, we show how the activation of wüstite-based precursors depends on promoter loading and activation pressure. In this work, we show how the activation of wüstite-based precursors depends on promoter loading and activation pressure. The study is complementary and combines catalytic test measurements, with TPR, detailed XRD analysis and high pressure quasi in situ TEM studies more
Hanna Türk, Franz-Philipp Schmidt, Thomas Götsch, Frank Girgsdies, Adnan Hammud, Danail Ivanov, Izaak C. Vinke, L.G.J. (Bert) de Haart, Rüdiger-A. Eichel, Karsten Reuter, Robert Schlögl, Axel Knop-Gericke, Christoph Scheurer, Thomas Lunkenbein
In this work, we have investigated the electrolyte-anode interface of solid state electrolysis cells using modern methods of electron microscopy, X-ray spectroscopy, first-principle calculations, and molecular simulation together with scientists from the Electronic Structure Group of the AC Department and the Theory Department of FHI. No classical interface was found, but a complexion. This intermediate phase is less crystalline than the two oxides and is depleted in Sr. This finding can be explained by the degraded periodicity of the oxygen sublattice. The study reveals a new structural picture of such interfaces and we hope to use this model in the future to better explain the origin of the structural instability. more
Liudmyla Masliuk, Franz-Philipp Schmidt, Walid Hetaba, Milivoj Plodinec, Gudrun Auffermann, Klaus Hermann, Detre Teschner, Frank Girgsdies, Annette Trunschke, Robert Schlögl, and Thomas Lunkenbein
(Mo,V)Ox is active and selective in the oxidative dehydrogenation of ethane to ethylene. Using EELS measurements, we have demonstrated differences between the surface and bulk compositions. Lateral surfaces are Mo-rich than bulk, whereas basal surfaces are V-rich. Different facets also have different compositions. This will have wide implications for the formation of the active structure and thus for catalysis. more
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