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Alkan, Baris ; Duarte-Correa, Liseth ; Girgsdies, Frank ; Koch, Gregor ; Kröhnert, Jutta ; Ertegi, Mervan ; Jiang, Shan ; Lunkenbein, Thomas ; Trunschke, Annette:
From “Single Sites” to Stable Nanoparticles Derived from Spray-Flame Synthesized Solid Solutions of Cobalt in MgO for Ammonia Decomposition.
In: ACS Catalysis.
Bd. 15
(2025)
Heft 7
.
- S. 5781-5795.
ISSN 2155-5435
DOI: https://doi.org/10.1021/acscatal.5c00187
Abstract
Chemical energy storage, in particular, the storage of hydrogen in carbon-free molecules such as ammonia, is being considered as an essential element in the transformation of our future energy system. In the present work, cobalt catalysts were investigated as alternatives to Ru- and Ni-based materials for the decomposition of ammonia. Spray-flame synthesis (SFS) was used to prepare metastable, phase-pure solid solutions Mg1-x Co x O, 0.03 <= x <= 0.47, as catalyst precursors composed of oxide nanoparticles with a particle size of 7-8 nm. In situ and operando XRD, H2-TPR studies, electron microscopy, Raman spectroscopy, and FTIR spectroscopy of adsorbed CO were applied to characterize the nanostructure of the host oxides and catalysts generated by exsolution of Co under reductive conditions. Calcination at 600 degrees C causes partial segregation of a Co3O4 spinel phase at a higher Co content (x >= 0.24). Small Co clusters are formed by exsolution from the solid solution, while the reduction of the spinel component yields Co nanoparticles of 3.3-8.5 nm. Very high space-time yields of 19 mmolH2 <middle dot>gcat -1<middle dot>min-1 at 500 degrees C can be achieved due to the high dispersion of metallic cobalt. The turnover frequency (TOF) for metallic nanoparticles in the range between 1 and 5 nm remains constant at about 0.2 s-1, suggesting a structure insensitivity of the reaction in this size range at industrially relevant reaction conditions (500 degrees C, 100% NH3, WHSV of 36,000 N mL<middle dot>g-1<middle dot>h-1, 1 atm) caused by structural dynamics. Only atomically dispersed cobalt shows a TOF of about 0.5 s-1. The Co/Mg1-x Co x O catalysts exhibit very good stability even at high Co contents under the harsh conditions of ammonia decomposition due to strong metal-support interaction, making continuous SFS, which is potentially scalable, an attractive method for preparing cost-effective and resource-saving catalysts for ammonia decomposition.
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| Publikationsform: | Artikel in einer Zeitschrift |
|---|---|
| Begutachteter Beitrag: | Ja |
| Zusätzliche Informationen: | WOS:001450939900001 |
| Institutionen der Universität: | Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie |
| Titel an der UBT entstanden: | Nein |
| Themengebiete aus DDC: | 500 Naturwissenschaften und Mathematik > 540 Chemie |
| Eingestellt am: | 12 Jun 2025 07:07 |
| Letzte Änderung: | 12 Jun 2025 07:07 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/93648 |