Model systems and nanoscale functional materials in catalysis

Group mission

Nanoparticles exhibit novel, size- and shape-dependent properties that open up a broad range of possibilities for their application as functional materials and catalysts. Precise control over material synthesis is therefore essential to tailor their quality and physicochemical properties. Our research focuses on the synthesis of well-defined nanoparticles and clusters in the liquid phase, which serve as a versatile toolbox for the development of model catalysts and functional magnetic materials. We use a broad range of chemical synthesis approaches in batch processes that enable precise control over particle size, shape, structure, and composition, while also addressing the transfer and scale-up of these syntheses to continuous flow processes.

Group objective

A central objective of our research is the development of well-defined model catalysts to establish fundamental relationships between catalyst composition, structure, and catalytic performance, thereby enabling the rational design of more efficient catalytic systems. We characterize the size, size distribution, morphology, surface area and composition of nanoparticles and catalysts using various techniques including electron microscopy (SEM, TEM, EDX), X-ray diffraction (XRD, SAXS), dynamic light scattering, FTIR, UV-vis and optical emission spectroscopy (ICP-OES) as well as classic surface sensitive methods (e.g., N₂ physisorption).

Group topics

Our current research focuses mainly on:

• Batch synthesis of novel, colloidal nanoparticles,

• Continuous flow manufacturing of nanoparticles, cluster compounds, and catalysts,

• Novel catalyst materials and structure-reactivity relationships in direct hydrogen peroxide synthesis, syngas chemistry and emission control catalysis.

Research topics and projects

Emission Control Catalysts Based on Noble Metal Clusters and Nanoparticles

Noble metal catalysts based on nanoscale particles are crucial for controlling emissions from hydrocarbon combustion (e.g., CO, NO_x, volatile organic compounds (VOCs), etc.). The high cost and scarcity of these metals present challenges, necessitating strategies that maximize catalytic efficiency while minimizing precious metal usage. Currently, catalyst preparation is mainly guided by empirical approaches rather than rational catalyst design. The aim is to develop a fundamental understanding of the relationship between catalyst structure and performance at the atomic scale, enabling the more rational design of catalysts that maximize the number of active sites and enhance the mass activity of these precious metal systems. To address this challenge, we develop novel mono- and multimetallic cluster compounds and colloidal nanoparticles (e.g., Pt, Pd, Rh and/or Ru) as precursors for the manufacturing of powder model catalysts for emission control applications (such CO, NO_x, CH₄ and VOC oxidation).

Related research project: CRC 1441

Continuous Flow Manufacturing of Cluster Compounds and Nanoparticles for Advanced Catalysis

Model catalysts derived from inorganic cluster and colloidal nanoparticles closely mimic real catalysts and are of particular interest for bridging the material and pressure gap between fundamental surface sciences and industrial applications. However, these compounds are typically synthesized via batch processes with high dilutions, making the scale-up time-consuming and the reproducibility challenging. Consequently, large-scale preparation of atom-defined clusters and nanoparticles remains at an early stage with immense challenges, limiting their broader application. To address these limitations and enable the design of modern structured catalysts with highly active and selective surface sites, we develop new processes for the continuous flow synthesis of mono- and multimetallic clusters and nanoparticles in solution.

To achieve precise control over particle characteristics, the influence of reaction parameters is investigated, while the particle formation kinetics is monitored online. The resulting clusters and nanoparticles are subsequently integrated into structured catalysts, e.g., into monoliths for emission control applications.

Related research project: CRC 1441

Novel Nanoparticle-Based Catalysts for Direct Hydrogen Peroxide Synthesis

The direct synthesis of hydrogen peroxide (H₂O₂) from O₂ and H₂ is an attractive alternative to the currently established anthraquinone process due to its atom efficiency and possibility for decentralized, on-demand production. However, further understanding and improvement of the process and the employed catalyst materials is required. Our research focuses on the development of model catalysts based on colloidal nanoparticles where the active metal is diluted down to the single atom level by a less active host metal. We investigate the influence of the electronic and geometric structure of the catalysts on their catalytic properties in the thermo-catalytic direct synthesis of hydrogen peroxide from molecular hydrogen and oxygen. By comparing these systems with the electrocatalytic two-electron reduction of oxygen to hydrogen peroxide, we aim to identify common structural motifs, active sites, and reaction mechanisms that govern catalytic activity and selectivity. This will enable improved catalyst design for both thermo-catalytic and electro-catalytic direct synthesis of hydrogen peroxide in the future.

Related research project: FOR 5715 "Bridging Concepts in Thermo- and Electro-Hydrogen Peroxide Catalysis" (HyPerCat)

Development of Novel, Bifunctional Catalysts for the Hydrogenation of Carbon Dioxide and Carbon Monoxide

We develop advanced catalyst materials for the conversion of CO and CO₂ into platform chemicals. A major focus of our research is the single-step synthesis of dimethyl ether (DME) from synthesis gas (syngas-to-dimethyl ether, STD) using bifunctional catalysts. This process represents a promising strategy for the efficient utilization of CO₂ and synthesis gas derived from biomass gasification and offers significant technical and economic advantages over the conventional two-step process.

To design high-performance catalysts, we develop bifunctional model catalysts based on well-defined nanoparticles. These model systems enable us to gain mechanistic insights and establish fundamental structure–property relationships in complex catalytic materials. The knowledge obtained provides the basis for the rational design of next-generation catalysts for the efficient conversion of CO and CO₂ into sustainable chemicals.

Related research project: MTET.

Functional Materials: Magnetic Nanoparticles and Nanocomposites

The magnetic behaviour of magnetic nanoparticles is strongly governed by their size, shape, and crystal structure. In particular, their incorporation into isotropic and anisotropic organic matrices such as technical oils, liquid crystals or polymers opens new perspectives for the development of functional magnetoresponsive materials, including ferrofluids, ferronematics, and magnetic heating systems, with applications across actuation, catalysis and energy technologies. Our research focuses on the synthesis of magnetic nanoparticles, including ferrites with spinel or magnetoplumbite structures as well as magnetic metals and alloys. Using different liquid-phase synthesis approaches, we tailor particle size, morphology (e.g., spheres, rods, platelets), and magnetic properties.

Currently, we address the continuous hydrothermal synthesis (CHTS) of magnetic nanoparticles in near- and supercritical water (scH₂O 347 °C, 22.1 MPa) as an environmentally friendly and scalable route. Supercritical water (374 °C, 22.1 MPa) combines liquid-like densities with mass transport properties intermediate between those of gases and liquids and provides a unique reaction medium with highly attractive characteristics for nanoparticle synthesis.

Equipment and methods