The interaction and adsorption of molecules, especially CO, on ceria surfaces is an important tool for probing the surface electronic structure and reactivity. In particular, the molecular vibrational frequencies and their shifts in different environments provide a direct way to distinguish these environments. The objective of the present work is to relate these frequencies and their shifts to the nature of the physical and chemical interactions between the adsorbate and substrate. This is done through a decomposition of the adsorbate-substrate interaction into contributions from the various terms that determine the adsorption energy and the C-O stretch vibrational frequency. The Constrained Space Orbital Variation, CSOV, methodology, where certain orbitals of the substrate and/or adsorbate are fixed or frozen and others are varied so that different contributions to the interaction can be selectively included or excluded, is used. The contributions of mechanisms that will be quantified include the effect of the electric field due to the ionic character of CeO<sub>2</sub>, and the contributions of dative covalent bonds between adsorbate and substrate. Furthermore, the role of the covalent character of the Ce cation, which leads to occupations of the 4f and 5d frontier orbitals and their consequences for the CO-ceria interaction will be examined. The interaction of CO with different Ce oxidation states will also be studied. The analysis is based the energies and properties of wavefunctions for cluster models of ceria.

Theoretical analysis of adsorption on ceria surfaces

2019 Fall National Meeting

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