Research Topics

Beyond catalytical activity, the electrochemical and structural stability is the crucial property that determines the applicability of promising electrocatalysts such as MoS₂-based nanomaterials. In our group,  we correlate electron microscopy imaging with operando electrochemical techniques to understand and prevent the mechanisms of degradation of MoS₂-based electrocatalysts for the hydrogen evolution reaction.
   

The development of novel electrocatalysts is essential for advancing sustainable energy technologies. Compositionally complex solid solutions (CCSS), which contain five or more elements, offer unique electrocatalytic properties due to their numerous active sites. While these diverse surface atomic arrangements (SAA) have the potential to overcome the limitations of conventional electrocatalysts, their intrinsic complexity and associated chemistry remain challenging to fully understand, presenting a hurdle for future applications.  

Over 60% of the produced energy is lost as heat, making advancements in heat recovery and management critical. High-performance thermoelectrics -promising for waste heat harvesting and refrigerant-free cooling- require a complex interplay of efficient electrical and poor thermal conduction. One approach to achieve this is microstructural engineering. However, how individual microstructural features affect the local thermal and electrical conductivity remains unclear.  

Two approaches have proven immensely successful in the design of new materials: thermodynamic description of crystalline phases, and manipulation of crystal defects. In the Collaborative Research Centre SFB1394 “Structural and Chemical Atomic Complexity: From Defect Phase Diagrams to Material Properties”, defects and their thermodynamic stability are brought together in the framework of defect phase diagrams.  

The sunlight is capable of answering the global energy need. Semiconducting materials have been developed to convert solar radiation into fuels for energy storage and mobile applications. Electronic band alignment, carrier transport, and reaction kinetics at interfaces make the system optimization a joint adventure for physicists, materials scientists, and chemists. In our group, we apply structural and electrochemical characterization to study nanostructured materials and their stabilities.  

To stop climate change, it is critical to decarbonize our energy system by replacing fossil fuels with greener alternatives. Fuel cell technology plays an important role in the transition to a world powered by renewable energy sources. This project focuses on investigating the degradation of polymer electrolyte membrane fuel cells during operation, one of the biggest issues for their widespread commercialization.  

Thermoelectric materials can convert largely untapped heat energy sources, e.g. geothermal or industrial waste heat, into sustainable electricity. Despite their high potential, efficient thermoelectrics are rare. High thermoelectric conversion efficiency requires high electrical conductivity (σ) but low thermal conductivity (κ), a rare combination in materials. Using materials science principles, these transport properties can be tailored by microstructural defects.  

Single-crystalline TiO₂ nanowires are utilized as stable support for iridium electrocatalysts. The local structure and interactions between the metal and the TiO₂ support are analysed by electron microscopy These analyses are correlated to the electrochemical activity, effectively establishing synthesis-structure-property relationships at sub-nanometer scale.   
   

Complex solid solution nanoparticles (often called high-entropy alloys) are promising catalyst for various energy application. Our research is dedicated to CrMnFeCoNi complex solid solution nanoparticles which possess a high activity towards oxygen reduction reaction thanks to the interplay of multi-elements active sites. An exceptionally high activity in alkaline media was found.  

Two-dimensional (2D) inorganic transition metal boride nanosheets are emerging materials for energy application due to their unique properties. Typical processing routes involve chemical etching of bulk material synthesized via solid-state reaction at temperatures above 1000 °C. In our work, we investigate the formation of MoB MBene domains in MoAlB thin films grown at 700 °C along with various other defects such as 90-degree twist boundaries and compositional defects.  

Nanostructured manganese oxides (MnO_x) can be applied in energy storage and catalysis. Thus, structure-property relationships are key for the rational design of efficient MnO_x functional nanomaterials. In this project, we stablish correlations between the local structure and chemistry and the electrochemical properties of iron manganese oxide (Fe_xMn_1-xO₂) nanosheets, nanowires and nanocones.
   

It is four decades that lanthanides doped semiconductors are used to generate light. The most interesting feature of lanthanide emission is their very sharp luminescent lines. It enables them to be used in various applications such as TV displays and solid-state lasers. This is due to 4f electrons being effectively shielded from the surrounding crystal field by the outer filled 5s and 5p shells. The 4f shell is not fully occupied which allows transitions to happen within the f orbital.  

Intelligent design of nanostructured materials forms the basis for high efficiencies in energy applications. 3D hierarchical niobium oxide nanostructures are investigated, as they form self-organized using a facile one-step synthesis approach. Electron microscopic investigations in combination with different spectroscopic methods are used to analyse these superstructures heading towards a better understanding of the forces involved in self-organization at the nanoscale.  

Understanding the atomic structure of functional nanomaterials and unraveling their impact on chemical reactions is important as it can provide guidelines for their improvement. In this study, low dimensional nanomaterials are synthesized using wet-chemical strategies and tested in various electrochemical reactions. Electron microscopy before and after the reactions allows to unravel the growth mechanism and the atomic arrangement as well as to identify degradation phenomena.