Forschungsprojekte

 

CO oxidation over Au catalysts

Supported gold catalysts are highly active for a variety of reactions including low-temperature CO oxidation. The current understanding of the mode of operation of such gold catalysts is still incomplete as important details such as the activation of oxygen or the role of oxygen vacancies are unknown. Currently we investigate the role of ceria as support material employing in situ Raman spectroscopy under reaction conditions. Read more

Structure of vanadia catalysts

Vanadia is of great interest due to its catalytic properties. We investigate the structural dynamics of supported vanadia catalysts in selective oxidation reactions using Resonance Raman spectroscopy. In combination with other methods such as IR, UV-Vis and X-ray photoelectron spectroscopy this allows us to propose structural models. Assignment of vibrational bands is facilitated by results from normal-mode analysis. Read more

 

NOx storage reduction

We explore the mechanism of NOx storage reduction using in situ Raman spectroscopy. For BaO materials exposure to NO2 at temperatures up to 400°C the formation of an intermediate barium-nitro phase precedes the formation of nitrate ions, which upon further exposure lead to the formation of bulk nitrates. Pre-oxidation of the catalyst or exposure to oxygen leads to the formation of peroxides which enhance the rate for nitrate formation while the formation of nitro species is suppressed above 300°C. Read more

Multi in situ spectroscopy

Multiple in situ spectroscopy allows to obtain information from various spectroscopic methods applied to one catalyst sample. We combined Raman, UV-Vis and X-ray photoelectron spectroscopy (XPS), within one experimental setup to study the effect of water on both structure and dispersion of vanadia based selective oxidation catalysts. Read more

Li-ion batteries

In situ Raman diagnostics are employed to unravel the mode of operation and mechanisms of fatigue of cathode materials for secondary Li ion batteries on a molecular level. The main focus of this project is on the oxide materials LixMOy (M = Co, Ni, Mn) as well as their binary and ternary mixtures. Wavelength dependent Raman spectroscopy is used to study the influence of resonance effects. Read more

Metal-oxide gas sensors

We study the metal-oxide gas sensing mechanism by correlating the sensor response with spectroscopic changes. For this purpose the sensor response to the target gas is measured simultaneously with different in situ spectroscopic techniques (Raman, IR, MS, UV/Vis). Thereby the feeding gas composition (target gas, oxygen, humidity, carbon dioxide), the sensor temperature, the sensor history and the sensor properties (surface area, grain size, doping) are changed to elucidate their influence on the sensing mechanism. Read more

Nanoscale structuring

For controlled synthesis and nanoscale structuring of surfaces we employ atomic-layer deposition (ALD). A unique feature of ALD is the possibility to form conformal uniform coatings on arbitrarily shaped materials with controlled atomic-scale thickness. We apply ALD to porous substrates with high specific surface areas thereby enabling novel applications, such as those in the fields of catalysis and alternative energy. Read more