O2 Activation on Ceria Catalysts—The Importance of Substrate Crystallographic Orientation. Issue 51 (23rd November 2017)

• Record Type: Journal Article
• Authors: Yang, Chengwu; Yu, Xiaojuan; Heißler, Stefan; Weidler, Peter G.; Nefedov, Alexei; Wang, Yuemin; Wöll, Christof; Kropp, Thomas; Paier, Joachim; Sauer, Joachim
• Is Part Of: Angewandte Chemie international edition. Volume 56:Issue 51(2017)
• Page Start: 16399
• Page End: 16404
• Publication Date: 2017-11-23
• Subjects: CeO2 -- dioxygen activation -- IRRAS -- surface chemistry -- vibrational spectroscopy; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201709199
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: An atomic‐level understanding of dioxygen activation on metal oxides remains one of the major challenges in heterogeneous catalysis. By performing a thorough surface‐science study of all three low‐index single‐crystal surfaces of ceria, probably the most important redox catalysts, we provide a direct spectroscopic characterization of reactive dioxygen species at defect sites on the reduced ceria (110) and (100) surfaces. Surprisingly, neither of these superoxo and peroxo species was found on ceria (111), the thermodynamically most stable surface of this oxide. Applying density functional theory, we could relate these apparently inconsistent findings to a sub‐surface diffusion of O vacancies on (111) substrates, but not on the less‐closely packed surfaces. These observations resolve a long standing debate concerning the location of O vacancies on ceria surfaces and the activation of O2 on ceria powders. Abstract : A puzzle is solved : The first infrared reflection–absorption spectroscopy (IRRAS) data of dioxygen activation on an oxide single‐crystal surface show, in conjunction with theory, the formation of various superoxo and peroxo species on reduced CeO2 (110) and (100) surfaces, but not on CeO2 (111). This inconsistency originates from a subsurface diffusion of O vacancies.