Periodic Reporting for period 2 - TACCAMA (Atomic-Scale Motion Picture: Taming Cluster Catalysts at the Abyss of Meta-Stability)
Reporting period: 2021-07-01 to 2022-12-31
In addition to the microscopic investigations, we also perform X-ray photoelectron spectroscopy (XPS) under identical conditions (same temperature, same gas composition and same pressure) so that we can correlate chemical with structural information. Finally, we use a pulsed reactivity setup to observe the reaction as it proceeds, i.e. monitor systematically the generation of different product molecules under the various conditions.
By using small clusters with a precisely defined number of atoms, we can investigate how highly reactive particle structures appear and disappear, how this process can be controlled, and how it influences the catalyst function. Essentially, in the regime of these very small, sub-nanometre particles, even the addition of a single atom can lead to a significant change in the stability and reactivity of the resulting catalyst. We thus anticipate this knowledge will lead to the development of more cost-effective alternatives to the precious metal catalysts commonly used today, e.g. by using only the particles with the optimal size.
The main achievements so far are centered predominantly around ultra-high-vacuum precursor studies, where we demonstrated several key points for the future progression of the project. First, we have shown that the combination of pulsed reactivity measurements and microscopy is highly effective in disentangling reaction mechanisms on well-defined model catalysts. Second, we have proven that video-rate STM and atom tracking are ideally suited to following diffusion processes directly, such as the motion of small metal particles or structural changes in the oxide support. Third, we have successfully transported size-selected metal clusters deposited in Munich to a synchrotron facility for measurements on these highly defined model catalysts. And fourth, we have successfully performed first proof-of-concept STM experiments under realistic reaction conditions.
We expect this project in the second funding period to provide us with fundamental insights into the parameters controlling model catalyst stability and reactivity. By identifying the most active particle sizes, we anticipate the production of more material efficient catalysts will be made possible. Furthermore, an atomic-scale understanding of mechanistic details of such catalytic processes is key to developing new, sustainable and energy efficient materials for industrial chemistry.