Water-assisted generation of catalytic interface: The case of interfacial Pt-FeO_x(OH)_y sites active in preferential carbon monoxide oxidation

The surface of supported heterogeneous catalysts often contains adsorbed water and hydroxyl groups even when water is not directly added to the reaction stream. Nonetheless, the reactivity of adsorbed water and hydroxyl groups is rarely considered. We demonstrate that water and hydroxyl groups can not only directly participate in the...

Towards low-cost PEM fuel cells: Interfacial effects and material dynamics of a non-PGM electrocatalyst

In this thesis several aspects of PEM fuel cells are discussed. From an atomic scale, e.g. crystal and electronic structure of a non-noble metal material, e.g. (H)zLiMn2O4 (protonated spinel lithium manganese oxide) for electrocatalysis and its dynamics, to meso-macro scale effects such as those concerning transport resistances at the membrane...

Operando spectroscopic methods to study electrochemical processes

Fossil resources are being depleted, while the concentration of CO2 in the atmosphere rises. There clearly is a strong and immediate need for a radical energy transition. Renewable energy is growing strongly as supplier of fossil-free electricity, but it needs large-scale and long-term storage options in order to be able to make a real impact on...

Monitoring and quantifying morphological and structural changes in electrode materials under operando conditions

X-ray absorption and small-angle x-ray scattering spectra were simultaneously acquired under operando conditions in a joined technique approach, for the first time applied in the field of energy storage materials. This approach allows one to closely follow the electronic and local structure evolution, as well as monitor and quantify the...

Copper sulfide derived nanoparticles supported on carbon for the electrochemical reduction of carbon dioxide

The electrocatalytic reduction of CO₂ to produce sustainable fuels and chemicals is attracting great attention. Cu-based catalysts can lead to the production of a range of different molecules, and interestingly the product selectivity strongly depends on the preparation history, although it is not fully understood yet why. We...

The electrochemical sodiation of sb investigated by Operando X-ray absorption and ¹²¹ sb mössbauer spectroscopy: What does one really learn?

In this study, we want to highlight the assets and restrictions of X-ray absorption spectroscopy (XAS) and Mössbauer spectroscopy for investigating the mechanism of the electrochemical reaction of antimony electrode materials vs. Na. For this, operando XAS was carried out during the first one and a half cycles, and the whole set of measured...

Light control of the nanoscale phase separation in heteroepitaxial nickelates

Strongly correlated materials show unique solid-state phase transitions with rich nanoscale phenomenology that can be controlled by external stimuli. Particularly interesting is the case of light–matter interaction in the proximity of the metal–insulator transition of heteroepitaxial nickelates. In this work, we use near-infrared laser light in...

Crystal-Field and Covalency Effects in Uranates: An X-ray Spectroscopic Study

The electronic structure of U^V- and U^VI-containing uranates NaUO₃and Pb₃UO₆was studied by using an advanced technique, namely X-ray absorption spectroscopy (XAS) in high-energy-resolution fluorescence-detection (HERFD) mode. Due to a significant reduction in core–hole lifetime broadening,...