Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 9: Focus Session: Frontiers in Reducible Oxide Surface Science I

O 9.6: Vortrag

Montag, 12. März 2018, 12:30–12:45, HFT-FT 131

Surface structure and reactivity of cerium oxide — •Chengwu Yang, Alexei Nefedov, Yuemin Wang, and Christof Wöll — Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany.

Ceria is becoming a ubiquitous constituent in catalytic systems for a variety of applications over the last forty years. The high catalytic activity is connected with its strong redox properties making ceria the ideal buffer system for oxygen in a catalytic process. The importance of this material has triggered numerous experimental and theoretical studies. The studies on bulk single crystal surfaces, however, are still scarce.

On a novel UHV-FTIRS we used carbon monoxide (CO) as probe molecule to detect the surface structure of ceria bulk single crystals and nanocrystals. Our results indicate that CO is capable of probing surface oxygen vacancies and distinguishing facet orientations. After the determination of ceria surface structure, the unexpected origin of photoreactivity of ceria has been investigated by monitoring the UV-induced decomposition of nitrous oxide (N2O) on well-defined single crystals of ceria. We demonstrate that ceria becomes photoactive only in the presence of surface O-vacancies with largely undercoordinated electron-rich Ce3+ cations. Additionally, we also provide direct spectroscopic evidence for the formation of active dioxygen species (superoxo and peroxo species) on the reduced ceria (110) and (100) surfaces upon oxygen (O2) adsorption. However, neither of these species was present on ceria (111).