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.
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.
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 stability.
TiO2 nanostructures are promising electrodes for dye or hybrid solar cells and are utilized as stable support for electrocatalyst. Among a great variety of nanostructures, single-crystalline TiO2 nanowires exhibit particularly interesting characteristics. In this project TiO2 nanowires are synthesized via a hydrothermal approach and analyzed using electron microscopy. The main focus is on the morphology changes during annealing and core etching which lead to better performance.
Multinary transition metal nanoparticles are promising candidates for energy applications. Our research is based on the synthesis and atomic-scale characterization of such multinary systems. The nanoparticles are prepared by sputtering of elements into ionic liquids. Depending on the synthesis conditions, they grow either in an amorphous or crystalline state. The amorphous particles can be transformed to different crystalline phases via electron beam bombardment or post annealing.
The progressing climate change and our increasing demand of energy supply combined with a decreasing stock of natural resources constrain us to focus on alternative, renewable energy suppliers. One of the many viable solutions therefore are fuel cells (FCs) which are devices that enable us to convert the chemical energy of a fuel into electrical energy via catalyzed reactions on electrodes. This project focusses on high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs).
It is four decades that lanthanides are being doped into semiconductors as a way to realize light emitters. 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. In fact, the 4f shell is not fully occupied which allows transitions to happen within the f orbital.
The CarMON project, short for Carbon Metal-Oxide Nanohybrids, is performed by the INP - Leibniz Institute for Plasma Science and Technology (Greifswald), the INM - Leibniz Institute for New Materials (Saarbrücken) and our group. Novel materials are developed by combining metal oxides and carbonaceous materials for electrochemical energy storage and water desalination. Synergistic effects on the nanoscale between these two material types can lead to overall increased performance.
In the light of growing energy needs, depleting fossil fuels, and the threatening global warming, alternative energy sources are needed. Chalcopyrite materials are suitable for renewable energy applications, for example solar cells, water splitting or photo catalysis. In our study, we synthesize copper indium disulfide films via a solvothermal procedure. The nanostructured films are crystalline even at temperatures below 200 °C as shown by electron microscopic techniques.
Thermoelectrics have attracted increasing attention as a sustainable and flexible source of electricity able to meet a wide range of power requirements. Their application is wide as they could be used in automotive, aerospace and medical fields, and wherever temperature gradients exist. In this project we focus mostly on the ternary Ag–Sb–Te system as it is a promising thermoelectric material. The investigated compounds possess moderate to high ZT-values depending on their microstructure.
Metals are ductile and ceramics are stiff. Ideally, these advantageous properties of each material class can be combined in one material. Examples are nanolaminated systems such as Mo2BC and Cr2AlC. In this project, we focus on the atomic level analysis of these materials using aberration corrected scanning transmission electron microscopy.
Thin films are used in a variety of technologies, e.g. as coatings or for microelectronic applications. Miniaturization and the eventually high surface to volume ratio might enhance thin film degradation. Understanding and controlling of the underlying processes will help to establish reliable and controlled devices or new scopes of application. In this project, we focus on well-defined aluminum thin films as model system and their solid state dewetting behavior.