Research
Our group concentrates on the preparation of heterogeneous catalysts and on their electrocatalytic evaluation. Especially important are high surface area materials with controllable size, facets and functional groups that are cost-efficient and scalable. Through a systematic approach of first characterizing model surfaces and then transferring them to nanoparticulate systems, we create the basis for application-oriented materials that can be used e.g. in fuel cells or electrolysers. Many of the fundamentals of both fields are very closely interlinked (surface potential, double layer, etc.) and we use the best of both worlds to obtain a deeper understanding of the catalytic processes and their underlaying reaction mechanisms. The catalytic reactions include the oxygen reduction reaction (ORR), the oxygen evolution reaction (OER), the hydrogen evolution reaction (HER) and the carbon dioxide reduction.
Our research is supported by fundamental studies on the growth mechanisms and the subsequent development of new materials. Innovative, automated characterization techniques are used to evaluate the catalysts' performance which enables the examination of numerous materials in a short time and thus accelerates the discovery of new materials. The corresponding reaction mechanisms that are essential for understanding the underlying processes are examined.
Synthesis of Nanomaterials
The ability to influence the nanostructure and composition of nanostructured catalysts during synthesis is a prerequisite for maintaining high-performance and long-term stable functional materials. In this sense, innovative, easily controllable and scalable synthetic routes for catalyst materials are of great interest. Core-shell materials for instance combine the properties of a particle core with those of a particle shell, can develop synergistic interactions, and also make it possible to significantly reduce the proportion of cost-critical components (e.g. precious metals).
Running (collaborative) projects include:
1. Deposition of monolayer thin metals onto non-noble elements to form core-shell structures
2. Synthesis of single atom catalysts for the electrochemical production of hydrogen peroxide
Further reading:
M. Ledendecker, S. Krick Calderón, C. Papp, H. P. Steinrück, M. Antonietti, M. Shalom, Angew. Chem. Int. Ed. 2015, 54, 12361-12365.
M. Ledendecker, E. Pizzutilo, G. Malta, G. V. Fortunato, K. J. Mayrhofer, G. J. Hutchings, S. J. Freakley, ACS Catalysis 2020.
Low Temperature Fuel Cells
In our low temperature fuel cell research activities, we concentrate on materials for the acidic proton exchange membrane (PEM) fuel cells (FC). In PEMFCs, the stability of non-noble and noble metals is still one of the main obstacles to overcome. We rely on innovative, automated characterization techniques which are used to evaluate the catalyst’s performance. This enables the examination of many materials in a short time and thus accelerates the discovery of new materials. We determine structure-performance parameter that are essential for understanding the underlying processes during catalysis.
Running (collaborative) projects include:
Non-carbon based supports that show sufficient conductivity and can withstand the harsh conditions of the ORR.
Core-shell nanoparticles and their behaviour during ORR.
Shape-controlled nanoparticles with defined facets for enhanced ORR kinetics.
Further reading:
D. Göhl, A. Garg, P. Paciok, K. J. Mayrhofer, M. Heggen, Y. Shao-Horn, R. E. Dunin-Borkowski, Y. Román-Leshkov, M. Ledendecker, Nat. Mater. 2020, 19, 287-291.
D. Jalalpoor, D. Göhl, P. Paciok, M. Heggen, J. Knossalla, I. Radev, V. Peinecke, C. Weidenthaler, K. J. J. Mayrhofer, M. Ledendecker, F. Schüth, J. Electrochem. Soc. 2021, 168, 024502.
J. Knossalla, P. Paciok, D. Gohl, D. Jalalpoor, E. Pizzutilo, A. M. Mingers, M. Heggen, R. E. Dunin-Borkowski, K. J. J. Mayrhofer, F. Schüth, M. Ledendecker, J. Am. Chem. Soc. 2018, 140, 15684-15689.
Low temperature electrolyzers
In our water electrolysis activities, we concentrate on the oxygen and hydrogen evolution side where the harsh conditions as low pH and high potentials (OER) pose substantial challenges to the stability of the catalysts. We explore material combinations to overcome one of the main obstacles: to reduce the amount of precious metals while keeping the stability high.
Running (collaborative) projects include:
1. The evaluation of core-shell materials for the oxygen evolution reaction based on IrO2 and non-noble cores
Further reading:
Patent: Beschichtung und ein Verfahren zum Herstellen von Kern-Schalen-Nanopartikeln, Daniel Göhl, Marc Ledendecker, DE 10 2021 118 226.3, 2021, Technische Universität Darmstadt
S. Geiger, O. Kasian, M. Ledendecker, E. Pizzutilo, A. M. Mingers, W. T. Fu, O. Diaz-Morales, Z. Li, T. Oellers, L. Fruchter, A. Ludwig, K. J. J. Mayrhofer, M. T. M. Koper, S. Cherevko, Nat. Catal. 2018, 1, 508-515.
M. Ledendecker, S. Geiger, K. Hengge, J. Lim, S. Cherevko, A. M. Mingers, D. Göhl, G. V. Fortunato, D. Jalalpoor, F. Schüth, C. Scheu, K. J. J. Mayrhofer, Nano Research 2019, 12, 2275-2280.
Electrocatalytic H2O2 production
Our group works actively on the electrocatalytic reduction of oxygen to H2O2. In classical heterogeneous catalysis, the selective production of H2O2 from molecular hydrogen and oxygen has been a target reaction since the beginning of the 20th century. Through electrochemical half-cell testing, both reactions can be investigated independently and conclusions for the heterogeneous synthesis of H2O2 can be drawn. Single atoms of palladium supported on high surface area carbon supports have demonstrated to be highly selective and active towards the production of H2O2. Here, we rely on strong collaboration partners from the field of classical heterogeneous catalysis (Simon Freakley, Graham Hutchings, Karl Mayrhofer and Ioannis Katsounaros).
Further reading:
M. Ledendecker, E. Pizzutilo, G. Malta, G. V. Fortunato, K. J. Mayrhofer, G. J. Hutchings, S. J. Freakley, ACS Catalysis 2020.
CO2 reduction
Coming soon...