New materials are the key to emerging technologies. Complex nanomaterials are the building blocks for new devices in molecular electronics (from organic field effect transistors to light emitting diodes) or in sensor technology; they hold the potential to improve the efficiency of energy conversion processes (e.g. in organic photovoltaics, fuel cells, or water splitting), help to advance energy storage technology (e.g. in chemical energy carriers, hydrogen storage, or batteries) and to improve catalytic processes (e.g. in hydrogenation, reforming, or environmental catalysis).
Most of the fascinating functionalities that we encounter in these complex materials arise from their interface properties. The conversion of light, chemical energy and electricity requires the transport either of electrons, of ions, of atoms, or of molecular species via phase boundaries. Building complex nanostructured materials, we can improve the efficiency of these processes or even implement entirely new functionalities. Up to date, however, the synthesis of such complex nanomaterials mostly relies on empirical trial-and-error approaches. With the materials getting more and more complex, progress is slowing down as can already be seen in many areas of nanotechnology. The key to eliminate the “materials bottleneck” is the knowledge-based development of new materials: We need to understand how transport and transformation processes work at the microscopic level, which factors limit their performance and, very importantly, why certain nanomaterials undergo degradation. Finally, we need to transfer this knowledge to the development of new devices.
Strategy and Mission:
Starting from this challenge, the research mission of our group aims at
a) understanding chemical transformations and physical properties of complex interface-controlled materials at the molecular scale and at
b) transferring this knowledge to real materials and real application conditions.
To this end we follow a three-step research strategy:
(I) Model approach to interface-controlled materials
Real materials and devices are outstandingly complex systems, both from a structural and from a chemical point of view, thereby preventing us from obtaining atomic-level insights in many cases. Model systems are the key to understand nanomaterials and their interfaces at the microscopic level. The idea of the model approach involves chemical or structural complexity introduced in a controlled fashion and under ultraclean conditions. This allows us to derive structure-functionality relationships at interfaces and nanostructures with atomic-precision control. In a second step, this knowledge can be transferred to real materials and conditions.
(II) Molecular and material complexity to build functional interfaces
Many functionalities of novel interface-controlled materials rely on interfaces between complex solid materials (nanostructured materials, porous materials, nanoparticles, mixed oxides or alloys, etc.) and complex molecular materials (functional organic units or molecules, carbon-based structures, etc.). Our research aims at building and characterizing such interfaces and at developing the spectroscopic tools to study them from ideal to real conditions.
(III) Connecting ideal and real systems or conditions
The third and, very often, the major challenge is the transfer of knowledge from ideal model experiments to real materials and application conditions. This implies that spectroscopic and microscopic methods have to be developed, for example to perform in-situ spectroscopy under ambient and high pressure conditions (e.g. molecular electronics and sensors, for hydrogen storage and energy-related catalysis) or under electrochemically controlled conditions (e.g. for photovoltaics, fuel cells and electrochemically controlled storage devices). We are currently performing electrochemical characterization and spectro-electrochemistry on both ideal (single crystal) and real (porous and thin film) electrocatalysts and electrode materials (liquid/solid interface), as well as operando spectroscopies (solid/gas interface) on ideal (model catalysts) and real nanomaterials (powders, pellets, porous films) from ultrahigh vacuum to high pressure conditions (currently up to 20 bars). Planned activities focus on further methods to transfer information between model experiments and real applications.