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Issue 14, 2012
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Oxygen transport and isotopic exchange in iron oxide/YSZ thermochemically-active materials via splitting of C(18O)2 at high temperature studied by thermogravimetric analysis and secondary ion mass spectrometry

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Abstract

Ferrites are promising materials for enabling solar-thermochemical cycles for the production of synthetic fuels. Such cycles utilize solar-thermal energy for the production of hydrogen from water, or carbon monoxide from carbon dioxide. Recent work studying the thermochemical behaviour of iron oxides co-sintered with yttria-stabilised zirconia (YSZ) using thermogravimetric analysis revealed a striking difference in behaviour of iron that is in solid solution with the YSZ and that which exists as a second iron oxide phase. Materials in which the majority of iron was dissolved in the YSZ exhibited enhanced utilization of iron over those which possessed larger fractions of un-dissolved, bulk iron oxides. To illuminate this phenomena further, several samples of thermally-reduced iron oxide/8YSZ were re-oxidised using isotopically labelled C(18O)2. Post mortem characterization by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), with the application of multivariate analysis tools, enables the differentiation between 18O and 16O signals emanating from iron oxide particles. The distribution of 18O is uniform throughout the iron-doped 8YSZ, but concentrated at the surface of iron oxide particles embedded in this matrix. After identical thermal reduction and re-oxidation treatments, the gradient of 18O/16O across the iron oxide particles is found to depend on the size of the iron oxide particles, as well as the method of synthesis of the iron oxide/YSZ material. Comparative thermogravimetric analyses of the 18O-labelled materials and analogous un-labelled materials revealed that exposure to CO2 at 1100 °C results in rapid oxygen isotopic exchange.

Graphical abstract: Oxygen transport and isotopic exchange in iron oxide/YSZ thermochemically-active materials via splitting of C(18O)2 at high temperature studied by thermogravimetric analysis and secondary ion mass spectrometry

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Supplementary files

Article information


Submitted
19 Oct 2011
Accepted
13 Feb 2012
First published
24 Feb 2012

J. Mater. Chem., 2012,22, 6726-6732
Article type
Paper

Oxygen transport and isotopic exchange in iron oxide/YSZ thermochemically-active materials via splitting of C(18O)2 at high temperature studied by thermogravimetric analysis and secondary ion mass spectrometry

E. N. Coker, J. A. Ohlhausen, A. Ambrosini and J. E. Miller, J. Mater. Chem., 2012, 22, 6726
DOI: 10.1039/C2JM15324F

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