Nanoscaled Materials for Catalytic Processes
Transition metal nanoparticles represent important materials in catalysis, not only in fundamental studies but also in various processes of great industrial and societal relevance. Although even small improvements in the catalytic properties of these materials can have a large economic or ecological impact, the processes/mechanisms that occur on the surface and the nature of the active site are often not understood or even known. However, a better understanding of these fundamentals is a prerequisite for rational design of catalysts with improved catalytic activity or selectivity. In this context, model catalysts with defined material properties can help to elucidate structure-property relationships.
We develop nanoparticles with tailored properties which we use as precursors for the production of defined model catalysts required for various reactions (precursor concept). The nanoparticles serve are employed as defined building blocks in a flexible toolbox to specifically tune the properties of the catalysts. The nanoparticles are usually immobilized on a support material to manufacture powder model catalysts. However, we also use the nanoparticles as quasihomogeneous catalysts dispersed in liquid carrier media (such as ionic liquids). Nanoparticle-based powder model catalysts may help to bridge the gap between fundamental surface science on single crystals and industrial application.
The development of high-quality nanoparticles and model catalysts requires a large repertoire of chemical synthesis methods which allow for the control of the material parameters. We make use of various synthesis strategies such as solvothermal, decomposition, polyol and reduction processes. We also exploit the specific physicochemical properties of ionic liquids to control nucleation/growth processes in the liquid phase and to stabilize nanoparticles by weakly coordinating anions/cations. We are particularly interested in metals, alloys, and intermetallic compounds. We use various analytical tools to characterize the size, shape, structure and composition of our nanoparticles and catalysts (see also equipment).
Figure 1. To study structure-properties-relationsships, we develop nanoparticles with tailored size, shape and composition and use them as precursors for manufacturing of model catalysts (precursor concept).
Our current focus is in particular on a better understanding of synthesis gas processes (one-step synthesis of dimethyl ether from synthesis gas (CO2/CO/H2) using bifunctional catalysts), selective hydrogenation of organic substrates in the liquid phase (quasihomogeneous catalysts in ionic liquids), and the direct synthesis of hydrogen peroxide from molecular hydrogen and oxygen. Here we operate various continuous, semi-continuous and batch reactors to study the catalytic properties as a function of different material parameters (size, shape, structure and composition). Within the framework of CRC 1441 „Tracking the Active Site in Heterogeneous Catalysis for Emission Control” we are also interested in the development of powder model catalysts for emission control.
Selected review article on this topic:
- D.I. Sharapa, D.E. Doronkin, F. Studt, J.-D. Grunwaldt, S. Behrens, Moving Frontiers in Transition Metal Catalysis: Synthesis, Characterization and Modeling, Adv. Mater. (2019), 31, 1807381
For further information see publications.