Redox Flow Batterien
Redox-flow batteries are a promising technology for large scale stationary energy storage applications. They offer chemical storage of electrical energy in the form of a vanadium electrolyte, whereby the stored energy is accessible at will. In comparison to other technologies, one major advantage of the redox-flow battery is the scalability of storage capacity via the employed electrolyte volume independent from the size of the cell.
Our group’s research is mainly focused on the characterization and optimization of commonly employed carbon based electrode materials. Besides the fabrication of nanostructured electrodes (by electrospinning) and of highly porous carbon composite materials (e.g. by salt templating), we also investigate the degradation of commercially available electrodes using electrochemical impedance spectroscopy.
CO2 emissions resulting from the excessive use of traditional energy sources, are the major contributor in global warming. In this respect, electrochemical CO2 conversion into valuable chemicals and fuels with enhanced energy density is a promising solution to mitigate these environmental changes as well as reduce our dependence on fossil fuels. Unfortunately, the CO2 electroreduction is significantly limited by its very low kinetics (i.e., high overpotential) as well as low energy efficiency, catalyst stability and product selectivity along with low faradaic efficiency. Thus, our research group is focusing on the design of efficient non-precious nanostructured electrocatalysts with unique morphologies (i.e., dendrites, flowers, etc) to overcome the inherent CO2 inactivity. Additionally, various advanced in-situ and operando spectroscopy techniques (e.g. XAS) are used to correlate the activity, selectivity and stability to the catalyst structure and reveal detailed chemical information about the catalyst–molecule interactions in real time.
The Electrospinning technique is an efficient approach to prepare nanofibers with high surface areas on a large scale. A broad range of organic polymers can be used to fabricate thin fibers, which could be used in redox flow batteries, fuel cells, and many other applications. In our group we modify this technique to prepare carbon fibers, metal containing fibers and also hollow fiber structures.
To generate hollow fibers a special electrospinning technique, the so called coaxial electrospinning, is used. By this modification two separate polymers flow through a coaxial double-capillary and generate a core-shell structure. After a subsequent treatment by washing or leaching porous or hollow structures can be obtained.
Fuel cells are a promising clean energy technology due to their high efficiency, low emissions, silent operation and modularity. Our research focuses on synthesis and investigation of catalyst materials for fuel cell relevant reactions. This includes (a) synthesis of structured precious (Pt, Ag) and non-precious catalysts (Ni,Co) materials via templating and colloidal methods for the oxidation of organic fuels and reduction of oxygen in half cell mode (b) spectroscopic investigations of CO interaction on Pt with different support materials by DRIFTS and (c) development of hybrid fuel cell concept for the investigation of Ni based catalyst towards oxygen reduction reaction in alkaline conditions as present in alkaline membrane fuel cells.