$Ce_{2/3}Cr_{1/3}O_{2+y}$: A New Oxygen Storage Material Based on the Fluorite Structure

Singh, Preetam and Hegde, MS and Gopalakrishnan, J (2008) $Ce_{2/3}Cr_{1/3}O_{2+y}$: A New Oxygen Storage Material Based on the Fluorite Structure. In: Chemistry Of Materials, 20 (23). pp. 7268-7273.

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Abstract

In an exploratory search for new oxygen storage materials (OSMs), we have identified a fluorite-type solid solution series, Ce1-x,CrxO2+y (0 < x <= 1/3), of which the x = 1/3 member, Ce2/3Cr1/3O2.11 (oxide I), exhibits excellent reversible oxygen release/storage properties at relatively low temperatures (similar to 350 degrees C). Oxide I prepared by a hydrothermal route crystallizes in a metastable nanocrystalline (similar to 4 nm) fluorite type structure (a = 5.352 angstrom) where the cerium and chromium are randomly distributed. Characterization of oxide I by electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, and thermgravimetry for the composition, crystal structure, oxidation states of metal atoms, and oxygen stoichiometry yields the formula (Ce2/3Cr1/9Cr2/9O2.10 +/- 0.02)-Cr-IV-Cr-VI0-O-IV for oxide I. Investigation of oxygen release/intake by temperature programmed hydrogen reduction and thermogravimetric studies has revealed that oxide I possesses a high oxygen storage capacity of 0.175 moles of O-2/mole up to 550 degrees C; this value is better than or comparable to the best OSMs based on CeO2-ZrO2. The temperature (similar to 350 degrees C) at which facile oxygen release/intake occurs with oxide I is also lower than that of CeO2-ZrO2 based oxides. Formation of oxide I with a cation-disordered fluorite structure, unlike other lanthanide analogs, and its oxygen release/storage properties are discussed in terms of the redox chemistry of Ce-IV/III and Cr-VI/IV in the solid state.

Item Type:	Journal Article
Publication:	Chemistry Of Materials
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	09 Mar 2009 08:34
Last Modified:	19 Sep 2010 04:58
URI:	http://eprints.iisc.ac.in/id/eprint/17852

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