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Research Papers

A Two-Step Thermochemical Water Splitting by Iron-Oxide on Stabilized Zirconia

[+] Author and Article Information
Tatsuya Kodama

Department of Chemistry & Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181, Japantkodama@eng.niigata-u.ac.jp

Yumiko Nakamuro, Takayuki Mizuno

Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181, Japan

J. Sol. Energy Eng 128(1), 3-7 (Dec 01, 2004) (5 pages) doi:10.1115/1.1878852 History: Received April 30, 2004; Revised December 01, 2004

The thermochemical two-step water splitting cycle was examined by using an iron oxide supported on yttrium-stabilized, cubic zirconia (YSZ) as the working material with a view toward direct conversion of solar high-temperature heat to clean hydrogen energy. In the first step of the cycle, the YSZ-supported Fe3O4 was thermally decomposed to the reduced phase at 1400°C under an inert atmosphere. The reduced solid phase was oxidized back to the original phase (the YSZ-supported Fe3O4) with steam to generate hydrogen below 1000°C. A new redox pair, which is different from the Fe3O4FeO pair previously examined by others, served as the working solid material on this YSZ-supported Fe3O4. Our new redox reaction proceeded as follows. The Fe3O4 reacted with YSZ to produce an Fe2+-containing ZrO2 phase by releasing oxygen molecules in the first step: The Fe2+ ions entered into the cubic YSZ lattice. In the second step, the Fe2+-containing YSZ generated hydrogen via steam splitting to reproduce Fe3O4 on the cubic YSZ support. This cyclic reaction could be repeated with a good repeatability of the reaction below 1400°C.

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Figures

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Figure 1

The experimental setup for the TR step

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Figure 2

XRD patterns of (a) the original Fe3O4(20wt%)∕YSZ, and (b) that after the TR step at 1400°C

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Figure 3

Time variations of hydrogen production rate per weight of material in the WO step of the first run. Symbols: Fe3O4(20wt%)∕YSZ (●) and pure YSZ (엯). The TR step was preformed at 1400°C. The sample weight was 1.0g.

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Figure 4

Evolved hydrogen amount in the WO step using Fe3O4∕YSZ. Symbols: Fe3O4(20wt%)∕YSZ (●) and Fe3O4(25wt%)∕YSZ (엯). The TR step was performed at 1400°C. The sample weight was 1.0g.

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Figure 5

Change in a (311) reflection peak of Fe3O4 in XRD patterns of (a) the Fe3O4(20wt%)∕YSZ original, (b) that after the TR step at 1400°C, and (c) that after the subsequent WO step.

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