Development of Reactive Ceramic Devices for High-Temperature Solar Thermo Water Splitting

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In this research project, we have developed reactive ceramic devices to be used in solar thermochemical two-step water splitting cycle, for utilizing high-temperature solar heat in sun-belt regions. The main results are listed below :1. Development of High Reactive Ceramic PowdersWe investigated the other-metal doping effect on the ferrite supported on zirconia and found that Ni_<0.1>Fe_<2.0>O_4/ZrO_2 is the most reactive powder. On the other hand, we also found that, when yttrium-cubic-stabilized zircionia or YSZ is used as support instead of normal monoclinic zirconia, an iron-containing YSZ or Fe^<2+>-YSZ is formed by a high-temperature reaction between YSZ, and FeBBB_<3B>OB_<4B> supported on the YSZ at 1400℃ in an inert atmosphere, and that the FePPP^<2+P>-YSZ then reacts with steam and generate hydrogen at 1000-1100℃, to form FeP^<3+P>-YSZ that is re-activated by a thermal reduction in a separate step at temperatures above 1400℃ under an inert atmosphere.2. Preparation and Reactivity Test of Reactive DevicesZirconia foams coated with the Ni<1.0>Fe_<2.0>O4/ZrO_2or Fe_3O_4/YSZ particles were prepared as reactive devices and examined on reactivity for two-step water splitting cycle being performed alternately at temperatures between 1100 and 1400℃. Hydrogen successfully continued to be produced in the repeated 13-30 cycles, but foam device had cracks and broken after the repeated cycles. Ceramic foams with a higher thermal shock resistance, such as SiC foam, should be used as the matrix of the reactive devices.3. Coating of SiC foam with Ziconia and Performance test for Thermal Resistance under Solar IrradiationThe SiC foam matrix was successfully coated with zirconia layers before FeBB_<3BB>OBB_<4BB> is applied on the matrix. On the other hand, the SiC foam matrix was examined on thermal resistance under solar irradiation using solar furnace and, as the results, we found that the SiC foam matrix has a good thermal resistance.