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Researchers from the Inorganic Chemistry Departments of the Fritz Haber Institute revealed how structural changes on the surface and in the bulk region of the cobalt oxide catalyst Co3O4 influence its selectivity in the production of industrially relevant chemicals like acetone. They discovered that a metastable, structurally “trapped” state exhibits the highest catalytic activity - an important finding for catalyst design.
Key Aspects
- Industrially relevant reaction: The study sheds light on the catalytic oxidation of isopropanol (2-propanol) to acetone, a chemical that is widely used in industry and laboratories.
- Insights into catalyst selectivity: The study reveals how the structure of the cobalt oxide catalyst Co₃O₄ and structural reorganization processes on its surface “at work” influence its catalytic performance.
- Optimizing catalysis: The highest activity and selectivity of the catalyst are observed when the catalyst is held in a unique metastable, “trapped” structural state - not in a stable, ideally ordered crystalline form.
- Rethinking catalyst design: The obtained insights may help develop more selective, efficient, and stable catalysts, thus reducing side-products, energy costs, and separation steps in industrial production of chemicals such as acetone.
Heterogeneous catalysis, a cornerstone of the chemical industry
From ammonia synthesis to plastics production, heterogeneous catalysis is a fundamental process in the chemical industry. The catalyst is often in solid form, while other reagents are liquid or gaseous, which is ideal for separating the reaction products at the end. Therefore, a great deal of research is being invested in the development and refinement of heterogeneous catalysts. This study emphasizes that findings regarding the processes on the catalyst surface must be taken into account.
The role of selectivity in catalysis
The ideal catalyst can preferentially promote a specific, desired reaction when multiple reactions are possible - it is selective. This property, that can be controlled through catalyst design, is crucial for industrial processes as it enhances product purity and saves energy, since it avoids cumbersome post-reaction product-separation processes. However, it often remains unclear what exactly determines selectivity at the molecular level. To understand this, the research team from our institute uses operando methods that allow them to observe the catalysts “at work.”
Gaining a new understanding of catalytic oxidation
In their recent study, the research team sheds light on a significant heterogeneously catalyzed industrial process in which selectivity plays an important role: the oxidation of isopropanol (2-propanol) to acetone using cobalt oxide (Co₃O₄) for thermal catalysis. They combine operando X-ray spectroscopy and operando transmission electron microscopy to get a deeper insight into the catalyst performance, particularly how it is influenced by the processes taking place on the catalyst surface and within its interior (the bulk region).
How do surface reactions influence catalyst performance?
The comparison of catalyst activity measurements in a reactor and the operando information about the structural changes during catalyst operation yield two activity phases: one below and one above 200 °C. At lower temperature, a network of solid-state processes such as diffusion and defect formation distort the catalyst structure, which controls the catalytic properties of Co3O4, while at higher temperature, crystal ordering dominates.
Interestingly, the ideal combination of activity and selectivity is found at 200 °C, namely at the boundary between the two phases. Here, the catalyst can be conceived to be trapped in a transition between two energetically equivalent states, where small changes to the conditions can cause the system to flip between these states. It is desirable to keep the catalyst in this state for optimized performance. This can be achieved by creating optimal working conditions, but might also be further enhanced by catalyst design and suitable pretreatment.
Significance of the findings
The findings of the study challenge conventional catalyst design. The study suggests that striving for a “perfect, stable” crystalline catalyst can sometimes be suboptimal. Rather, the authors show here that surface structural changes critically determine the activity and selectivity of oxidation catalysts. Their methodology - combining operando spectroscopy, microscopy and activity measurements - sets a benchmark for how to study catalysts under realistic conditions, capturing dynamic behavior that is invisible in commonly used analysis.
Finally, the study even suggests a shift in how chemists should think about heterogeneous catalysis: Catalyst surfaces should no longer be perceived just static, but as dynamic materials where internal restructuring, defect chemistry, and metastable transitions strongly matter.
Dr. Thomas Götsch, goetsch@fhi-berlin.mpg.de
https://www.nature.com/articles/s41929-025-01449-9
https://www.fhi.mpg.de/2192824/2026-01-16_Catalyst-selectivity-as-balancing-act
Microscope images from the operando TEM experiments: Changes of the surface structure of the catal ...
Copyright: © FHI
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Microscope images from the operando TEM experiments: Changes of the surface structure of the catal ...
Copyright: © FHI
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