25 November 2025
How do catalysts form – and why do they lose activity over time? An international group of researchers from Forschungszentrum Jülich, the University of Stuttgart, the Karlsruhe Institute of Technology, and other institutions has addressed these questions at the atomic scale. Using advanced in-situ electron microscopy, the scientists directly observed how metal nanoparticles form, evolve, and can potentially be stabilized. By employing atomically resolved secondary electron imaging, they correlated the stability of catalytic centers with local imperfections in the catalyst support.
Catalysts are essential for energy technologies such as fuel cells and green hydrogen production. A promising new class – metal exsolution catalysts – offers improved performance for many applications but suffers from degradation over time. The studies, published in Nature Communications and Advanced Materials, reveal fundamental mechanisms of this degradation and show how crystal defects can act as anchoring sites that immobilize nanoparticles, thereby preventing their migration and extending catalyst lifetimes.
These results mark a significant advance in understanding mass transport in catalytic oxides at atomistic length scales. The team developed model catalysts with well-defined structures, combining advanced oxide synthesis and state-of-the-art electron microscopy – showcasing the materials expertise and analytical capabilities at Forschungszentrum Jülich and its partners.
The first study in Nature Communications used an environmental scanning transmission electron microscope (STEM) to visualize nanoparticle coarsening mechanisms at up to 700 °C. By combining surface-sensitive secondary electron and subsurface-sensitive high angle annular dark field imaging, the researchers directly linked nanoparticles to the atomic structure of their support. They demonstrated that subsurface defects hinder particle motion, enhancing stability, and achieved direct visualization of Ostwald ripening processes at the atomic scale.
In the second study in Advanced Materials, the team introduced dislocations into exsolution-active oxides by growing thin films on plastically deformed substrates. These dislocations served as preferential nucleation sites for nanoparticle formation. The resulting particles were observed directly above dislocations, confirming that dislocation engineering enables the controlled synthesis of defect-associated nanoparticles with improved stability. This approach may allow tailoring of catalytic properties through intentional introduction of crystal defects.
The findings have major implications for heterogeneous catalysis and renewable energy. Exsolution-active catalysts are particularly relevant for hydrogen production, where enhanced durability could significantly lower costs. By showing that structural defects can be deliberately engineered to stabilize nanoparticles, the team provides a route to more robust and efficient catalyst systems.
The work consisted of a collaboration between several institutes at the Forschungszentrum Juelich, including the Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C-2), the Peter Grünberg Institute (PGI-7) and the Institute of Energy Materials and Devices (IMD-2). The two studies were initiated at the Forschungszentrum Juelich by lead authors Dr. Dylan Jennings and Dr. Moritz L. Weber. Close collaborations were established with Prof. Xufei Fang of the Karlsruhe Institute of Technology, and Dr. Moritz Kindelmann of the Forschungszentrum Juelich. Additional contributions from authors at the Institute for Energy Technologies (IET-2), at the University of Stuttgart, and at the Colorado School of Mines, USA, were integral to the projects.
D. Jennings, M.L. Weber, A. Meise, T. Binninger, C.J. Price, M. Kindelmann, I. Reimanis, H. Matsumoto, P. Cao, R. Dittmann, P.M. Kowalski, M. Heggen, O. Guillon, J. Mayer, F. Gunkel, W. Rheinheimer
Direct atomic-scale investigation of the coarsening mechanisms of exsolved catalytic Ni nanoparticles
Nat. Commun. (2025), DOI: 10.1038/s41467-025-61971-z
M.L. Weber, M. Kindelmann, D. Jennings, J. Hölschke, R. Dittmann, J. Mayer, W. Rheinheimer, X. Fang, F. Gunkel
Atomic-Scale Insights into Nanoparticle Exsolution at Dislocations in Dislocation-Engineered Catalysts
Adv. Mater. (2025), DOI: 10.1002/adma.202502362
