Equilibrium oxygen storage capacity of ultrathin CeO2-δ depends non-monotonically on large biaxial strain

Elastic strain is being increasingly employed to enhance the catalytic properties of mixed ion–electron conducting oxides. However, its effect on oxygen storage capacity is not well established. Here, we fabricate ultrathin, coherently strained films of CeO 2-δ between 5.6% biaxial compression and 2...

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Published in:Nature communications 2017-05, Vol.8 (1), p.15360-15360, Article 15360
Main Authors: Balaji Gopal, Chirranjeevi, García-Melchor, Max, Lee, Sang Chul, Shi, Yezhou, Shavorskiy, Andrey, Monti, Matteo, Guan, Zixuan, Sinclair, Robert, Bluhm, Hendrik, Vojvodic, Aleksandra, Chueh, William C.
Format: Article
Language:English
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140/146
639/638/161/886
639/766/119/544
639/925/357/537
Chemical Sciences
Humanities and Social Sciences
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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Materialkemi
Materials Chemistry
MATERIALS SCIENCE
multidisciplinary
Natural Sciences
Naturvetenskap
Science
Science (multidisciplinary)
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Summary:Elastic strain is being increasingly employed to enhance the catalytic properties of mixed ion–electron conducting oxides. However, its effect on oxygen storage capacity is not well established. Here, we fabricate ultrathin, coherently strained films of CeO 2-δ between 5.6% biaxial compression and 2.1% tension. In situ ambient pressure X-ray photoelectron spectroscopy reveals up to a fourfold enhancement in equilibrium oxygen storage capacity under both compression and tension. This non-monotonic variation with strain departs from the conventional wisdom based on a chemical expansion dominated behaviour. Through depth profiling, film thickness variations and a coupled photoemission–thermodynamic analysis of space-charge effects, we show that the enhanced reducibility is not dominated by interfacial effects. On the basis of ab initio calculations of oxygen vacancy formation incorporating defect interactions and vibrational contributions, we suggest that the non-monotonicity arises from the tetragonal distortion under large biaxial strain. These results may guide the rational engineering of multilayer and core–shell oxide nanomaterials. The surface oxygen storage capacity is an important metric of catalytic activity, but its dependence on strain is not well characterized. Here, the authors show the surface oxygen nonstoichiometry in coherently strained CeO2-δ films increases non-monotonically with biaxial strain.
ISSN:2041-1723
2041-1723
DOI:10.1038/ncomms15360