Issue 8, 2011

High resolution mapping of surface reduction in ceria nanoparticles

Abstract

Surface reduction of ceria nano octahedra with predominant {111} and {100} type surfaces is studied using a combination of aberration-corrected Transmission Electron Microscopy (TEM) and spatially resolved electron energy-loss spectroscopy (EELS) at high energy resolution and atomic spatial resolution. The valency of cerium ions at the surface of the nanoparticles is mapped using the fine structure of the Ce M4,5 edge as a fingerprint. The valency of the surface cerium ions is found to change from 4+ to 3+ owing to oxygen deficiency (vacancies) close to the surface. The thickness of this Ce3+ shell is measured using atomic-resolution Scanning Transmission Electron Microscopy (STEM)-EELS mapping over a {111} surface (the predominant facet for this ceria morphology), {111} type surface island steps and {100} terminating planes. For the {111} facets and for {111} surface islands, the reduction shell is found to extend over a single fully reduced surface plane and 1–2 underlying mixed valency planes. For the {100} facets the reduction shell extends over a larger area of 5–6 oxygen vacancy-rich planes. This finding provides a plausible explanation for the higher catalytic activity of the {100} surface facets in ceria.

Graphical abstract: High resolution mapping of surface reduction in ceria nanoparticles

Article information

Article type
Paper
Submitted
19 May 2011
Accepted
02 Jun 2011
First published
30 Jun 2011

Nanoscale, 2011,3, 3385-3390

High resolution mapping of surface reduction in ceria nanoparticles

S. Turner, S. Lazar, B. Freitag, R. Egoavil, J. Verbeeck, S. Put, Y. Strauven and G. Van Tendeloo, Nanoscale, 2011, 3, 3385 DOI: 10.1039/C1NR10510H

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