Solar Hydrogen Productivity of Ceria–Scandia Solid Solution Using Two-Step Water-Splitting Cycle

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Chong-il Lee ◽  
Qing-Long Meng ◽  
Hiroshi Kaneko ◽  
Yutaka Tamaura
Keyword(s):  
Solid Solution ◽  
Water Splitting ◽  
High Performance ◽  
Oxygen Vacancies ◽  
Reaction Rate ◽  
Lattice Distortion ◽  
Complex Method ◽  
Solar Hydrogen ◽  
H2 Generation ◽  
Solar Hydrogen Production

The reactivity of CeO2–Sc2O3 solid solution for solar hydrogen production via two-step water-splitting reaction has been studied in this work. The CeO2–Sc2O3 solid solution was synthesized by polymerized complex method (PCM) with various Sc content between 0 and 20 mol. %. Analysis results from online direct gas mass spectrometry (DGMS) suggest that Ce3 + formed by CeO2–Sc2O3 solid solution in the O2-releasing step could be completely oxidized by H2O to generate hydrogen and return to Ce4 + in the H2-generation step. A Ce0.97Sc0.03O1.985 generates the largest amount of O2 and H2 among present samples, and the reduction and oxidation ratios are about 9.9% (Ce) and 10% (Ce), respectively. An estimated H2-generation reaction rate is about 4 ml g−1min−1 for Ce0.97Sc0.03O1.985. This value is about seven times greater than that of Ce0.89Zr0.11O2. The high reaction rate of Ce0.97Sc0.03O1.985 makes all formed Ce3 + completely oxidized by H2O in 5 min in the H2-generation step. The reasons for high performance are discussed from the views of lattice distortion and the amount of oxygen vacancies formed in the lattice.

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

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Hideyuki Ishihara ◽  
Hiroshi Kaneko ◽  
Noriko Hasegawa ◽  
Yutaka Tamaura
Keyword(s):  
Thermal Stability ◽  
Solid Solution ◽  
Hydrogen Production ◽  
Water Splitting ◽  
Solar Hydrogen ◽  
H2 Generation ◽  
Concentrated Solar Energy ◽  
Solar Hydrogen Production ◽  
Gas Volume ◽  
Splitting Process

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 (YSZ∕NiFe2O4 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 YSZ∕NiFe2O4 solid solution. The YSZ∕NiFe2O4 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 YSZ∕NiFe2O4 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, 1.9cm3∕g) and the generated H2 gas volume (the average H2 gas, 3.8cm3∕g) 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 YSZ∕NiFe2O4 solid solution, NiFe2O4 and ZnFe2O4, it is concluded that the YSZ∕NiFe2O4 solid solution is superior to the others.

H2 Generation by Two-Step Water Splitting With CeO2-MOx Using Concentrated Solar Thermal Energy

Solar Energy ◽  
2006 ◽  
Author(s):  
Hiroshi Kaneko ◽  
Hideyuki Ishihara ◽  
Takao Miura ◽  
Hiromitsu Nakajima ◽  
Noriko Hasegawa ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Thermal Energy ◽  
Infrared Imaging ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Solar Simulator ◽  
Solar Hydrogen ◽  
H2 Generation ◽  
Solar Hydrogen Production

CeO2-MOx (M = Mn, Fe, Ni, Cu) reactive ceramics, having high melting points and high conductivities of O2−, were synthesized with the combustion method from their nitrates for solar hydrogen production. The prepared CeO2-MOx samples were solid solutions between CeO2 and MOx with the fluorite structure through XRD. Two-step water splitting reactions with CeO2-MOx reactive ceramics proceeded at 1573–1773K for the O2 releasing step and at 1273K for the H2 generation step by irradiation of infrared imaging furnace as a solar simulator. The amounts of O2 evolved in the O2 releasing reaction with CeO2-MOx and CeO2 systems increased with the increase of the reaction temperature. The amounts of H2 evolved in the H2 generation reaction with CeO2-MOx systems except for M = Cu were more than that of CeO2 system after the O2 releasing reaction at the temperatures of 1673 and 1773K. The largest amount of H2 was generated with CeO2-NiO after the O2 releasing reaction at 1573, 1673 and 1773K. The O2 releasing reaction at 1673K and H2 generation reaction at 1273K with CeO2-Fe2O3 were repeated four times with the evolving of O2 (1.3cm3/g-sample) and H2 (2.3cm3/g-sample) gases, respectively. The possibility of solar hydrogen production with CeO2-MOx (M = Mn, Fe, Ni) reactive ceramics system by using concentrated solar thermal energy was suggested.

Hydrogen Production Through Two-Step Water Splitting Using YSZ (Ni,Fe) System for Solar Hydrogen Production

Solar Energy ◽  
2005 ◽  
Author(s):  
Hideyuki Ishihara ◽  
Hiroshi Kaneko ◽  
Tsutomu Yokoyama ◽  
Akinori Fuse ◽  
Noriko Hasegawa ◽  
...  
Keyword(s):  
Solid Solution ◽  
Hydrogen Production ◽  
Water Splitting ◽  
Gas Flow ◽  
Molar Ratio ◽  
Iron Ions ◽  
Solar Hydrogen ◽  
Solar Hydrogen Production ◽  
Ar Gas ◽  
Splitting Process

The two-step water splitting with the solid solution of YSZ (Yttrium stabilized Zirconia) and Ni-ferrite (NiFe2O4) was studied for solar hydrogen production. The sample of YSZ/Ni-ferrite solid solution was prepared by calcination of the mixture of the YSZ balls and Ni-ferrite (NiFe2O4) powder. The two-step water splitting process composed of O2-releasing reaction (T = 1773K) in Ar gas flow and H2-generation reaction (T = 1473K) in Ar gas and steam flow with the YSZ/Ni-ferrite solid solution were repeated ten times, and the molar ratio of the released O2 gas and the generated H2 gas was nearly equal to 1:2 in each cycle, indicating that the two-step water splitting process proceeded stoichiometrically. The lattice constants of the YSZ/Ni-ferrite solid solution products after each step of the water splitting process were varied, therefore it was assumed that the oxidation and reduction of the iron ions proceeded in the YSZ phase. It is confirmed that the YSZ/Ni-ferrite was the solid solution and reactive ceramics of high thermal stability. The contents of iron ions determined by the atomic absorption spectroscopy indicated that the YSZ/Ni-ferrite solid solution heated at 1773K contained the only 36% of iron loaded initially. The generated O2 gas was 42% of the theoretical yield. These suggest that YSZ/Ni-ferrite solid solution is more effective reactive ceramics which has the ability to split water with concentrated solar heat than Ni-ferrite.

Solar H2 Production With Tokyo Tech Rotary-Type Solar Reactor to be Tested Using Solar Concentration System at CSIRO in Australia

2009 ◽  
Author(s):  
Hiroshi Kaneko ◽  
Chong-il Lee ◽  
Yosuke Ishikawa ◽  
Koichiro Hosogoe ◽  
Yutaka Tamaura
Keyword(s):  
Solid Solution ◽  
Water Splitting ◽  
Reaction Temperature ◽  
Asia Pacific ◽  
Complex Method ◽  
Solar Simulator ◽  
H2 Generation ◽  
Solar Reactor ◽  
Test Operation ◽  
Rotary Type

The test operation of the Tokyo Tech rotary-type solar reactor (2nd model) is scheduled to be carried out using the solar concentrating system of CSIRO (New castle, Australia) as an international collaboration research between Japan (Tokyo Tech) and Australia (CSIRO) in APP (Asia-Pacific Partnership on Clean Development and Climate) project. The rotary-type solar reactor is positioned at an elevation of about 17 m. The input of solar power for the test operation is planned to be 50 kW from the solar concentrating system with about 10 heliostats. The estimation of evolved H2 gas was calculated from the amount of evolved O2 gas and the energy conversion efficiency is evaluated from the estimated amount of evolved H2 gas and the input of solar energy. The two-step water splitting process with the reactive ceramics of ceria-based solid solution (0.8CeO2−0.2ZrO2 prepared by the polymerized complex method) was investigated using the solar simulator of concentrated Xe lamp beams for the test operation of the rotary-type solar reactor at CSIRO solar concentrating system. The amounts of O2 and H2 gases evolved in the two-step water splitting reaction with CeO2-ZrO2 solid solution were determined for the H2-generation reaction temperatures of 773, 1273 and 1473 K. The amounts of evolved H2 gas decreased with an increase of the reaction temperature, however, the lowering of H2 gas evolution at 1473 K was 20% in comparison with that at 773 K. The heating time of the reactive ceramics up to the O2-releasing reaction temperature is evaluated to 3 s, when the difference between the O2-releasing reaction temperature (1773 K) and the H2-generation reaction temperature (1473 K) is 300 K.

Reactive Ceramics of CexSc1−xO2−Δ for Solar Hydrogen Production by Two-Step Water Splitting

2011 ◽  
Author(s):  
Chong-il Lee ◽  
Qing-long Meng ◽  
Hiroshi Kaneko ◽  
Yutaka Tamaura
Keyword(s):  
Water Splitting ◽  
Impedance Measurement ◽  
Oxygen Storage ◽  
Molar Ratio ◽  
Doped Ceria ◽  
Storage Process ◽  
Solar Hydrogen ◽  
H2 Generation ◽  
Anion Site ◽  
Solar Hydrogen Production

This paper describes the enhancement of the H2-generation reactivity by Sc doping in the CeO2. The evolved O2 gas (3.48ml/g) and H2 gas (7.00ml/g) for Ce0.97Sc0.03O1.985 are higher than those of Ce0.9Zr0.1O2, indicating that Sc-doping enhances the two step water splitting reactivity compared to the Zr-doping. The molar ratio of the H2 and O2 gases is nearly two, which suggests nearly completion of each step reaction for the H2O decomposition. The O2-releasing reactivity of Sc-doped ceria (Ce0.97Sc0.03O1.985) is nearly the same as that of Zr-doped one (Ce0.9Zr0.1O2), whereas the H2-generation reactivity is much different due to improvement of the H2-generation reactivity by Sc-doping. To examine the reason for the improvement, the ionic conductivity of Sc-doped and Zr-doped ceria has been measured with AC impedance spectroscopy. The activation energies of bulk conduction estimated from the impedance measurement are 1.09eV (Sc-doped) and 1.48eV (Zr-doped), respectively, in the temperature range of 400–800°C. This indicates that the oxygen deficient site movement of the Sc-doped ceria is more active than Zr-doped ceria. It could be said that the anion site can move more readily toward the surface of the ceramics by Sc-doping. This would facilitate the oxygen storage process (the H2-generation reaction).

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