Issue 25, 2020

A hybrid-DFT investigation of the Ce oxidation state upon adsorption of F, Na, Ni, Pd and Pt on the (CeO2)6 cluster

Abstract

The formation of small polarons in CeO2−x compounds has been investigated mainly on solids, compact surfaces, and large nanoparticles. However, those findings cannot be easily transferred to small ceria clusters, where size effects might play a crucial role. In this work, we report a hybrid density functional theory investigation within the Heyd–Scuseria–Ernzerhof functional to elucidate the response of the Ce oxidation state upon the adsorption of F, Na, Ni, Pd, and Pt on the (CeO2)6 cluster. Among the selected species, only the Na and Ni adatoms contribute to the formation of a single small-polaron neighboring the CeIII+ cation (i.e., change from CeIV+ to CeIII+) accompanied by a local distortion in the cluster structure, which can be explained by the large magnitude of the charge transfer from the adatoms to the cluster and change in the nature of the Ce f-states (delocalized to localized). The same effect is also obtained by adding a single electron to the (CeO2)6 cluster. The Pd and Pt adatoms yield only small charge transfer to the (CeO2)6 cluster, which is not enough to affect the Ce oxidation state. As expected, F binds to the cationic Ce sites and leads to the same effects as obtained by removing a single electron from the cluster, which implies the formation of a localized hole with O p-character above the highest occupied molecular orbital accompanied also by a local structural distortion; however, it does not affect the Ce oxidation state.

Graphical abstract: A hybrid-DFT investigation of the Ce oxidation state upon adsorption of F, Na, Ni, Pd and Pt on the (CeO2)6 cluster

Supplementary files

Article information

Article type
Paper
Submitted
28 Dec 2019
Accepted
18 May 2020
First published
25 May 2020

Phys. Chem. Chem. Phys., 2020,22, 14099-14108

A hybrid-DFT investigation of the Ce oxidation state upon adsorption of F, Na, Ni, Pd and Pt on the (CeO2)6 cluster

M. S. Ozório, K. F. Andriani and J. L. F. Da Silva, Phys. Chem. Chem. Phys., 2020, 22, 14099 DOI: 10.1039/C9CP07005B

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