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Technical Briefs

Two-Step Water Splitting Process With Solid Solution of YSZ and Ni-Ferrite for Solar Hydrogen Production (ISEC 2005-76151)

[+] Author and Article Information
Hideyuki Ishihara, Hiroshi Kaneko, Noriko Hasegawa

Research Center for Carbon Recycling Energy, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552, Japan

Yutaka Tamaura

Research Center for Carbon Recycling Energy, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552, Japanytamaura@chem.titech.ac.jp

J. Sol. Energy Eng 130(4), 044501 (Sep 08, 2008) (3 pages) doi:10.1115/1.2969813 History: Received May 09, 2005; Revised November 28, 2007; Published September 08, 2008

Ni-ferrite (NiFe2O4) is a promising reactive ceramics of the ferrite for the solar hydrogen production by a two-step water splitting process using concentrated solar energy. However, it should be pretreated before H2-generation reaction by grinding the Ni-ferrite sintered after the O2-releasing reaction to make a fine powder. If the Ni-ferrite and yttria stabilized zirconia (YSZ) form a solid solution between these oxides (YSZNiFe2O4 solid solution=YSZ(Ni,Fe)), it is expected that the two-step water splitting process with the Ni-ferrite system can proceed without treatment of the reduced product because of the high thermal stability of the YSZNiFe2O4 solid solution. The YSZNiFe2O4 solid solution was prepared by calcination of the mixture of the YSZ balls and NiFe2O4 powder at T=1823K for 1h, and its reactivity and thermal stability were examined for the two-step water splitting process. During the ten times repetition of the two-step water splitting reaction (T=1773K for O2-releasing, and 1473K for H2-generation) with the YSZNiFe2O4 solid solution using infrared imaging furnace, the reactivity for O2-releasing and H2-generation was kept constant. The molar ratio of the released O2 gas volume (the average O2 gas, 1.9cm3g) and the generated H2 gas volume (the average H2 gas, 3.8cm3g) was nearly 1:2, indicating that the water decomposition process via two steps proceeds. The X-ray diffractometry (XRD) measurement showed that the YSZ(Ni,Fe) keeps the YSZ phase structure during the ten times repetition of the two-step water splitting process. The successive H2 gas production by the two-step water splitting process was performed (ten times repetition of the two-step water splitting process). From comparative study on the reactivity and the thermal stability for the two-step water splitting reaction among the YSZNiFe2O4 solid solution, NiFe2O4 and ZnFe2O4, it is concluded that the YSZNiFe2O4 solid solution is superior to the others.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

Direct gas mass spectrometer (DGMS) signal of the O2-releasing reaction (a) and the H2-generation reaction (b)

Grahic Jump Location
Figure 2

The XRD patterns of the mixture of YSZ ball and Ni-ferrite (a), the YSZ(Ni,Fe) obtained by calcinations in air (b), the solid sample after the 10th H2-generation reaction in Ar gas and steam flow (c), and the solid sample after the 11th O2-relreasing reaction in Ar gas flow (d)

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