Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 32: Heterogeneous Catalysis I
O 32.6: Vortrag
Dienstag, 18. März 2025, 11:45–12:00, H25
How does lanthanum promote cobalt for ammonia synthesis in Co/La2O3 catalysts? — •Clara C. Aletsee, Lau H. Wandall, Ke Zhang, Oliver Christensen, Jens K. Nørskov, and Ib Chorkendorff — Physics, Technical University of Denmark
The interest in developing catalysts for ammonia synthesis, operating under milder reaction conditions than the Haber-Bosch process, has increased in the last decades. Cobalt, typically unreactive, can be activated for ammonia synthesis through the addition of lanthanum in metallic or oxidized form.1,2 To obtain a comprehensive understanding of the promotion mechanism, we investigate the ammonia formation over Co particles on La2O3 by combining experiments with theory. For this, we synthesized defined model catalyst, consisting of mass-selected Co nanoparticles, deposited on La2O3 films generated by magnetron sputtering. Their catalytic activity was tested at 1 bar and 350-500∘C in a UHV-compatible reaction cell.3 Catalyst states before and after reaction were analyzed by X-ray photoelectron spectroscopy and low-energy ion scattering. The results, combined with previous findings on the Co/LaN system,2 suggest that the reaction proceeds on La-promoted Co steps due to spin-mediated effects supported by theoretical calculations.4 We further demonstrate that the activity of the Co/La2O3 can be partially recovered after air exposure.
1S. I. Miyahara et al., ACS Omega 7, 24452-24460 (2022). 2K. Zhang et al., Science 383, 1357-1363 (2024). 3K. Zhang et al., Rev. Sci. Instrum. 94, 114102 (2023). 4A. Cao et al., Nat. Commun. 13, 2382 (2022).
Keywords: ammonia; lanthanum; cobalt; thermal catalysis; single crystal