Školitel: RNDr. Peter Matvija, Ph.D.
Stav práce: volná
Anotace:
Catalysts, substances that increase the rate and selectivity of chemical reactions without undergoing any permanent chemical change, are directly or indirectly involved in the production of about 90% of all chemicals and materials. Catalysts based on cerium oxide (ceria, CeO2) are highly effective due to their ability to switch between Ce3+ and Ce4+ states [1]. This property, also known as oxygen storage capacity (OSC) [2], arises from point defects in the material, which include missing ions (vacancies), excess ions (interstitials) or foreign kind ions (substitutional dopants).
Generation of increased density of point defects via inclusion of foreign atoms in the ceria structure has been a strategy for fine-tuning catalytic properties of ceria for a long time. For instance, incorporation of metal additives, M = Zr, Fe, Ni, Cu etc., into the ceria generally leads to an increase in the OSC. This increase can be explained by the fact that while oxygen storage in undoped CeO2 is restricted to the surface, there is usually participation of bulk oxygen in the storage process of Ce-based mixed oxides [3]. The increase in OSC may also be influenced by other factors such as the formation of local metal-ceria compounds or oxygen spillover [3].
In previous research, industrial ceria-based materials have primarily been studied as relatively complex powder catalysts. These catalysts possess a high active surface area, facilitating the quantification of their activity and the optimization of their composition through trial-and-error methods. However, the inherent complexity of these powder samples complicates the precise assessment of the reaction mechanisms underlying their catalytic activity.
In this thesis we aim to prepare well-defined model epitaxial layers of ceria grown on single-crystal samples (e.g. Cu(111), Pt(111)). These layers will be modified by additional deposition or co-deposition of other metals. These surfaces will then be characterized using in-situ/operando spectroscopic and atomically resolved microscopic methods (NAP-XPS/UPS, NAP-STM/AFM) [4, 5]. Results of these cutting-edge experimental techniques combined with theoretical calculations will help us gain more comprehensive understanding of the mechanisms that govern the behavior of these catalysts in reactive environments, paving the way for the development of more efficient catalysts.