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Nanocrystalline cerium-bismuth oxides : synthesis, structural characterization, and redox properties
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Sardar, Kripasindhu, Playford, Helen Y., Darton, Richard J., Barney, Emma R., Hannon, Alex C., Tompsett, David, Fisher, Janet M., Kashtiban, Reza J., Sloan, Jeremy, Ramos, S. (Silvia), Cibin, Giannantonio and Walton, Richard I. (2010) Nanocrystalline cerium-bismuth oxides : synthesis, structural characterization, and redox properties. Chemistry of Materials, Vol.22 (No.22). pp. 6191-6201. doi:10.1021/cm1025848 ISSN 0897-4756.
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Official URL: http://dx.doi.org/10.1021/cm1025848
Abstract
The hydrothermal oxidation of Ce3+ in basic aqueous solution by (NaBiO3)-O-V at 240 degrees C produces fine powders of cerium-bismuth oxides with crystallite sizes of less than 10 nm, as observed by transmission electron microscopy (TEM). Analysis of X-ray absorption near-edge structure at the Bi L-III and Ce L-III edges confirms the reduction of Bi5+ to Bi3+ and the oxidation of Ce3+ to Ce4+, consistent with a general chemical composition (Ce1-xBixO2-(x/2))-Bi-IV-O-III (x <= 0.6) for the mixed oxides. The refined cubic lattice parameters from powder neutron diffraction indicate a fluorite-like solid solution with volume that increases with Bi content. Pair distribution functions derived from total neutron scattering yield estimated values for refined particle diameters that agree with TEM, showing a decreasing crystallite diameter with increasing bismuth content, and a full analysis reveals that despite average long-range structure being described well as a fluorite solid-solution, the local structure is distorted. Thus, the short-range structure can be simulated as a mixture of symmetric eight-coordinate Ce sites, as seen in CeO2, and distorted Bi sites, as seen in beta-Bi2O3. Temperature programmed reduction studies reveal a large hydrogen uptake in the mixed oxides, which is reproducible on a second subsequent cycle. In situ powder XRD under hydrogen flow, however, reveals that this is due to partial phase separation to give bismuth metal. After six cycles, a material of initial composition Ce0.5Bi0.5O1.75 is completely phase-separated and its hydrogen uptake is reduced with high-resolution TEM analysis confirming the permanent reduction of the sample.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QD Chemistry T Technology > TA Engineering (General). Civil engineering (General) |
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||
Library of Congress Subject Headings (LCSH): | Cerium oxides -- Synthesis, Cerium oxides -- Structure, Oxidation-reduction reaction, Nanostructured materials | ||||
Journal or Publication Title: | Chemistry of Materials | ||||
Publisher: | American Chemical Society | ||||
ISSN: | 0897-4756 | ||||
Official Date: | 23 November 2010 | ||||
Dates: |
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Volume: | Vol.22 | ||||
Number: | No.22 | ||||
Number of Pages: | 11 | ||||
Page Range: | pp. 6191-6201 | ||||
DOI: | 10.1021/cm1025848 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Funder: | Engineering and Physical Sciences Research Council (EPSRC) | ||||
Grant number: | EP/F012721 (EPSRC) |
Data sourced from Thomson Reuters' Web of Knowledge
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