Comparison Studies of Reactivity on Nickel-Ferrite and Cerium-Oxide Redox Materials for Two-Step Thermochemical Water Splitting Below 1400°C

2011 ◽  
Author(s):  
Tatsuya Kodama ◽  
Nobuki Imaizumi ◽  
Nobuyuki Gokon ◽  
Tsuyoshi Hatamachi ◽  
Daiki Aoyagi ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Water Splitting ◽  
Cerium Oxide ◽  
Nickel Ferrite ◽  
Thermal Reduction ◽  
Monoclinic Zirconia ◽  
Reduction Step ◽  
Water Decomposition ◽  
Decomposition Step ◽  
Supported Ni

A two-step thermochemical water splitting cycle using a redox system of non-volatile metal oxide is one of the promising processes for converting concentrated solar high-temperature heat into clean hydrogen in sun-belt regions. In the 1st step of the cycle or the thermal reduction step, metal oxide is thermally reduced to release oxygen molecules in an inert gas atmosphere at a higher temperature above 1400°C. In the second step or the water-decomposition step at a lower temperature, the thermally-reduced metal oxide reacts with steam to produce hydrogen. As the reactive redox metal oxide materials to be capable of working below 1400°C, nickel-doped iron oxides or Ni-ferrites supported on zirconia, and non-stoichiometric cerium oxides are the promising working materials. In the present work, a series of the nickel-ferrite redox materials of monoclinic-zirconia-supported, cubic-YSZ(yttrium-stabilized zirconia)-supported, and non-supported Ni-ferries and non-stoichiometric cerium oxide were compared on reactivity for two-step thermochemical water splitting cycle. The monoclinic-zirconia-supported Ni-ferrite produced the most quantity of hydrogen in the repeated cycles when the thermal reduction step was performed for 30 min at 1400°C and the water decomposition step for 60 min at 1000°C.

New Solar Water-Splitting Reactor With Ferrite Particles in an Internally Circulating Fluidized Bed

2007 ◽  
Author(s):  
Nobuyuki Gokon ◽  
Shingo Takahashi ◽  
Hiroki Yamamoto ◽  
Tatsuya Kodama
Keyword(s):  
Metal Oxide ◽  
Fluidized Bed ◽  
Water Splitting ◽  
Circulating Fluidized Bed ◽  
Thermal Reduction ◽  
Solar Irradiation ◽  
Solar Water Splitting ◽  
Oxide Particles ◽  
Efficient Heat Transfer ◽  
Reactor Operating

The thermal reduction of metal oxides as part of a thermochemical two-step water splitting cycle requires the development of a high temperature solar reactor operating at 1000–1500°C. Direct solar energy absorption by metal-oxide particles provides efficient heat transfer directly to the reaction site. This paper describes experimental results of a windowed thermochemical water-splitting reactor using an internally circulating fluidized bed of the reacting metal-oxide particles under direct solar irradiation. The reactor has a transparent quartz window on the top as aperture. The concentrated solar radiation passes downward through the window and directly heats the internally circulating fluidized bed of metal-oxide particles. Therefore, this reactor needs to be combined with a solar tower or beam down optics. NiFe2O4/m-ZrO2 (Ni-ferrite supported on zirconia) particles is loaded as the working redox material in the laboratory scale reactors, and thermally reduced by concentrated Xe-beam irradiation. In a separate step, the thermally-reduced sample is oxidized back to Ni-ferrite with steam at 1000°C. As the results, the conversion of ferrite reached about 44% of maximum value in the reactor by 1kW of incident solar power. The effects of preheating temperature and particle size of NiFe2O4/m-ZrO2 were tested for thermal reduction of internally circulating fluidized bed in this paper.

New Solar Water-Splitting Reactor With Ferrite Particles in an Internally Circulating Fluidized Bed

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Nobuyuki Gokon ◽  
Shingo Takahashi ◽  
Hiroki Yamamoto ◽  
Tatsuya Kodama
Keyword(s):  
Metal Oxide ◽  
Fluidized Bed ◽  
Water Splitting ◽  
Circulating Fluidized Bed ◽  
Thermal Reduction ◽  
Beam Irradiation ◽  
Solar Water Splitting ◽  
Oxide Particles ◽  
Efficient Heat Transfer ◽  
Reactor Operating

The thermal reduction of metal oxides as part of a thermochemical two-step water-splitting cycle requires the development of a high-temperature solar reactor operating at 1000–1500°C. Direct solar energy absorption by metal-oxide particles provides direct efficient heat transfer to the reaction site. This paper describes the experimental results of a windowed small reactor using an internally circulating fluidized bed of reacting metal-oxide particles under direct solar-simulated Xe-beam irradiation. Concentrated Xe-beam irradiation directly heats the internally circulating fluidized bed of metal-oxide particles. NiFe2O4∕m‐ZrO2 (Ni-ferrite on zirconia support) particles are loaded as the working redox material and are thermally reduced by concentrated Xe-beam irradiation. In a separate step, the thermally reduced sample is oxidized back to Ni-ferrite with steam at 1000°C. The conversion efficiency of ferrite reached 44% (±1.0%), which was achieved using the reactor at 1kW of incident Xe lamp power. The effects of preheating temperature and NiFe2O4∕m‐ZrO2 particle size on the performance of the reactor for thermal reduction using an internally circulating fluidized bed were evaluated.

Hydrogen Production by Solar Thermochemical Water-Splitting/Methane-Reforming Process

Solar Energy ◽  
2003 ◽  
Author(s):  
Tatsuya Kodama ◽  
Yoshiyasu Kondoh ◽  
Atsushi Kiyama ◽  
Ken-Ich Shimizu
Keyword(s):  
Hydrogen Production ◽  
Metal Oxide ◽  
Water Splitting ◽  
Thermal Energy ◽  
Experimental Studies ◽  
Reduction Process ◽  
Thermal Reduction ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Solar Thermochemical

Two different routes of solar thermochemical hydrogen production are reviewed. One is two-step water splitting cycle by using a metal-oxide redox pair. The first step is based on the thermal reduction of metal oxide, which is a highly endothermic process driven by concentrated solar thermal energy. The second step involves water decomposition with the thermally-reduced metal oxide. The first thermal reduction process requires very-high temperatures, which may be realized in sun-belt regions. Another hydrogen production route is solar reforming of natural gas (methane), which can convert methane to hydrogen via calorie-upgrading by using concentrated solar thermal energy. Solar reforming is currently the most advanced solar thermochemical process in sun belt. There is also possibility for the solar reforming to be applied for worldwide solar concentrating facilities where direct insolation is weaker than that in sun belt. Our experimental studies to improve the relevant catalytic technologies are shown and discussed.

Existence of Cubic ZrO2 at 300°C on Bulk Zirconium

1969 ◽  
Vol 27 ◽  
pp. 166-167
Author(s):  
R.A. Ploc
Keyword(s):  
Metal Oxide ◽  
Metal Substrate ◽  
Preferred Orientation ◽  
Monoclinic Zirconia ◽  
Epitaxial Relationship

The manner in which ZrO2 forms on zirconium at 300°C in air has been discussed in the first reference. In short, monoclinic zirconia nucleates and grows with a preferred orientation relative to the metal substrate. The mode of growth is not well understood since an epitaxial relationship which gives minimum misfit between the zirconium ions in the metal/oxide combination is not realized. The reason may be associated with a thin cubic or tetragonal layer of ZrO2 between the inner oxygen saturated metal and the outer monoclinic zirconia.

Combinatorial Fabrication and High-Throughput Characterization of Thin Film Metal Oxide Libraries for Solar water Splitting

2018 ◽  
Author(s):  
Alfred Ludwig ◽  
Mona Nowak ◽  
Swati Kumari ◽  
Helge S. Stein ◽  
Ramona Gutkowski ◽  
...  
Keyword(s):  
Thin Film ◽  
Metal Oxide ◽  
Water Splitting ◽  
High Throughput ◽  
Solar Water ◽  
Solar Water Splitting
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