Do you want to keep up to date? Subscribe to our newsletter. 1 mail every 2 months! |
 |
Cerdanyola del Vallès (Barcelona), 21st June 2023. Catalysis research is one of the most exciting fields today, being of outmost importance for many industrial processes.
Gold nanoclusters catalysts are great candidates for several type of reactions, including the oxidation of carbon monoxide (CO). Their applications are countless and very useful, such as eliminating carbon monoxide in enclosed air environments, controlling vehicles' emissions or purifying hydrogen through water-gas shift reaction.
However, the role of ligands in these catalysts (the molecules that bind to the central metal atom) is still not fully understood.
Researchers from the Institute of Materials Chemistry of the Technical University of Vienna (TU Wien), led by researcher Noelia Barrabés, have now discovered the impact of different ligands to the core structure evolution of gold clusters supported on ceria (CeO2).
They analyzed the state and evolution of three different clusters structures in size and composition at different stages using complementary techniques.
At the NOTOS beamline of the ALBA Synchrotron, they performed extended X-ray absorption fine structure (EXAFS) studies during oxidative pretreatment and CO oxidation reactions. NOTOS is a hard X-ray beamline devoted to X-ray absorption spectroscopy and X-ray diffraction at the service of scientific disciplines like chemistry, catalysis, energy science, nanomaterials or environmental science. Using NOTOS, researchers were able to identify the structural changes having place in the gold nanoclusters. The analysis was complemented with X-ray Photoelectron Spectroscopy (XPS) and previous operando infrared studies.
Researchers found out that the reactivity of the gold nanoclusters is significantly influenced by the changes happening at the interface between the support, the ligands and the cluster core during pretreatment and reaction conditions. However, over 250 ºC, the reaction was similar regardless of the original cluster size and ligand composition. In fact, most of the gold nanoclusters appeared free of ligands from 200 ºC onwards. At 300 ºC a structural change took place including the formation of smaller nanoparticles, coinciding with a significant increase in CO oxidation activity.
These results show the high mobility of atoms in such small and precise metal nanostructures, with multiple factors affecting them. They are particularly relevant as they can be extended to other metal particle catalysts.
a) Schematics of the CO oxidation process involving gold (Au) cluster. b) Fourier Transform of EXAFS data, c) CO conversion and d) XPS bands collected on the catalysts at different stages of the process, e) experimental setup and f) picture of the users in NOTOS (ALBA Synchrotron).
NOTOS beamline is co-funded by the European Regional Development Fund (ERDF) within the Spanish Pluri-Regional Operative Programme (former Smart Growth Operative Programme) 2014-2020.
With the collaboration of Fundación Española para la Ciencia y la Tecnología. The ALBA Synchrotron is part of the of the Unidades de Cultura Científica y de la Innovación (UCC+i) of the FECYT and has received support through the FCT-21-17088 project.
