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O: Fachverband Oberflächenphysik

O 20: Oxides II: Structures, Interactions and Reducibility

O 20.5: Vortrag

Montag, 16. März 2020, 16:45–17:00, WIL B321

High temperature reduction and reoxidation of cerium oxide on Cu(111) — •Linus Pleines¹, Lars Buß^1,4, Tevfik Onur Menteş², Francesca Genuzio², Andrea Locatelli², Jan Ingo Flege⁴, and Jens Falta^1,3 — ¹Institute of Solid State Physics, University of Bremen, Germany — ²ELLETRA Synchrotron Light Source, Basovizza, Italy — ³MAPEX Center for Materials and Processes, Bremen, Germany — ⁴Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus-Senftenberg, Germany

Cerium oxide is of great interest due to its technological importance in various electronic, optical and catalytic applications. The inverse model catalyst cerium oxide on Cu(111) shows a high activity for the production of methanol. For the production of methanol from CO₂ and H₂ oxygen vacancies, e.g. in form of reduced ceria, are necessary. The reduction of ceria may be achieved by exposure to H₂ at elevated temperatures. We studied the interaction of H₂ and CO₂ with cerium oxide islands on a Cu(111) substrate with low-energy electron mircoscopy (LEEM) and x-ray absorption spectroscopy (XAS). From earlier studies the orientation of the CeO_x is known to be decisive for the catalytic activity. In our experiments both orientations are directly compared via growth of (100) and (111) CeO_x islands side by side on the same metal substrate, so that the same conditions prevail during the experiment. At high temperatures, exposure to H₂ leads to partial reduction and exposure to CO₂ leads to complete reoxidation of the cerium oxide. The (100) and (111) orientations show different reduction and reoxidation behaviours.