• Title/Summary/Keyword: Two-step water splitting

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Hydrogen Production with High Temperature Solar Heat Thermochemical Cycle using CeO2/ZrO2 Foam Device (CeO2/ZrO2 Foam Device를 이용한 고온 태양열 열화학 싸이클의 수소 생산)

  • Lee, Jin-Gyu;Seo, Tae-Beom
    • Journal of the Korean Solar Energy Society
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    • v.34 no.6
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    • pp.11-18
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    • 2014
  • Two-step water splitting thermochemical cycle with $CeO_2$ foam device was investigated by using a solar simulator composed of 2.5 kW Xe-Arc lamp and mirror reflector. The hydrogen production of $CeO_2$ foam device depending on reaction temperature of Thermal-Reduction step and Water-Decomposition step was analyzed, and the hydrogen production of $CeO_2$ and $NiFe_2O_4/ZrO_2$ foam devices was compared. As a result, the amount of reduced $CeO_2$ considerably varies according to the reaction temperature of Thermal-Reduction step. and hydrogen production was not much when the amount of reduced $CeO_2$ decreased even if the reaction temperature of Water-Decomposition step was high. Therefore, it is very important to keep the reaction temperature of Thermal-Reduction step high in two-step thermochemical cycle with $CeO_2$.

2-Step Thermochemical Water Splitting on a Active Material Washcoated Monolith Using a Solar Simulator as Heat Source (인공태양을 이용한 모노리스 적용 반응기에서 2단계 열화학적 물분해 연구)

  • Kang, Kyoung-Soo;Kim, Chang-Hee;Park, Chu-Sik
    • Transactions of the Korean hydrogen and new energy society
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    • v.18 no.2
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    • pp.109-115
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    • 2007
  • Solar energy conversion to hydrogen was carried out via a two-step thermochemical water splitting using metal oxide redox pair. To simulate the solar radiation, a 7 kW short arc Xe-lamp was used. Partially reduced iron oxide and cerium oxide have the water splitting ability, respectively. So, $Fe_3O_4$ supported on $CeO_2$ was selected as the active material. $Fe_3O_4/CeO_2$(20 wt/80 wt%) was prepared by impregnation method, then the active material was washcoated on the ceramic honeycomb monolith made of mullite and cordierite. Oxygen was released at the reduction step($1673{\sim}1823\;K$) and hydrogen was produced from water at lower temperature($873{\sim}1273\;K$). The result demonstrate the possibility of the 2-step thermochemical water splitting hydrogen production by the active material washcoated monolith. And hydrogen and oxygen was produced separately without any separation process in a monolith installed reactor. But the SEM and EDX analysis results revealed that the support used in this experiment is not suitable due to the thermal instability and coating material migration.

The Properties of the Several Metal Oxides in the Water-splitting for H2 Production (물 분해 수소제조를 위한 금속산화물들의 반응특성)

  • Son, Hyun-Myung;Park, Chu-Sik;Lee, Sang-Ho;Hwang, Gab-Jin;Kim, Jong-Won;Lee, Jin-Bae
    • Transactions of the Korean hydrogen and new energy society
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    • v.14 no.3
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    • pp.268-275
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    • 2003
  • The water-splitting process by the metal oxides using solar heat is one of the hydrogen production method. The hydrogen production process using the metal oxides (NiFe2O4/NiAl2O4,CoFe2O4/CoAl2O4, CoMnNiFerrite, CoMnSnFerrite, CoMnZnFerrite, CoSnZnFerrite) was carried out by two steps. The first step was carried out by the CH4-reduction to increase activation of metal oxides at operation temperature. And then, it was carried out the water-splitting reaction using the water at operation temperature for the second step. Hydrogen was produced in this step. The production rates of H2 were 110, 160, 72, 29, 17, $21m{\ell}/hr{\cdot}g-_{Metal\;Oxide}$ for NiFe2O4/NiAl2O4, CoFe2O4/CoAl2O4, CoMnNiFerrite, CoMnSnFerrite, CoMnZnFerrite, CoSnZnFerrite respectively in the second step. CoFe2O4/CoAl2O4 had higher H2 production rate than the other metal oxides.

A Study on Hydrogen Production with High Temperature Solar Heat Thermochemical Cycle by Heat Recovery (열회수에 따른 고온 태양열 열화학 싸이클의 수소 생산에 관한 연구)

  • Cho, Ji-Hyun;Seo, Tae-Beom
    • Journal of the Korean Solar Energy Society
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    • v.37 no.2
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    • pp.13-22
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    • 2017
  • Two-step water splitting thermochemical cycle with $CeO_2/ZrO_2$ foam device was investigated by using a solar simulator composed of 2.5 kW Xe-Arc lamp and mirror reflector. The hydrogen production of $CeO_2/ZrO_2$ foam device depending on heat recovery of Thermal-Reduction step and Water-Decomposition step was analyzed, and the hydrogen production of $CeO_2/ZrO_2$ and $NiFe_2O_4/ZrO_2$ foam devices was compared. Resultantly, the quantity of hydrogen generation increased by 52.02% when the carrier gas of Thermal-Reduction step is preheated to $200^{\circ}C$ and, when the $N_2/steam$ is preheated to $200^{\circ}C$ in the Water-Decomposition step, the quantity of hydrogen generation increased by 35.85%. Therefore, it is important to retrieve the heat from the highly heated gases discharged from each of the reaction spaces in order to increase the reaction temperature of each of the stages and thereby increasing the quantity of hydrogen generated through this.

Partial Reduction and Water Splitting Characteristics of Metal Substituted Ferrite Mediums for Thermochemical Hydrogen Production (열화학 수소 제조를 위한 금속 치환 페라이트 매체의 부분 환원 및 물 분해 특성)

  • Lee, Dong-Hee;Kim, Hong-Soon;Cha, Kwang-Seo;Park, Chu-Sik;Kang, Kyung-Soo;Kim, Young-Ho
    • Transactions of the Korean hydrogen and new energy society
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    • v.18 no.4
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    • pp.356-364
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    • 2007
  • The partial reduction and water splitting properties of metal substituted ferrite mediums for two-step thermochemical hydrogen production, were carried out by TPR/O(Temperature programmed reduction/oxidation) method at a temperature of below 1173 K and under atmospheric pressure. $ZrO_2$ was added to the ferrite as a binder to prevent the sintering. As the results, the reactivity of the metal species added to the ferrite mediums decreased in the order of Cu>Co>Ni>Mn, on the basis of water-splitting temperature. It was also found that the produced hydrogen amounts in the water-splitting step on partial reduced mediums were corresponding to the consumed hydrogen amounts in the previously partial reduction step.

Hydrogen Evolution from Biological Protein Photosystem I and Semiconductor BiVO4 Driven by Z-Schematic Electron Transfer

  • Shin, Seonae;Kim, Younghye;Nam, Ki Tae
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.251.2-251.2
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    • 2013
  • Natural photosynthesis utilizes two proteins, photosystem I and photosystem II, to efficiently oxidize water and reduce NADP+ to NADPH. Artificial photosynthesis which mimics this process achieve water splitting through a two-step Z-schematic water splitting process using man-made synthetic materials for hydrogen fuel production. In this study, Z-scheme system was achieved from the hybrid materials which composed of hydrogen production part as photosystem I protein and water oxidizing part as semiconductor BiVO4. Utilizing photosystem I as the hydrogen evolving part overcomes the problems of existing hydrogen evolving p-type semiconductors such as water instability, expensive cost, few available choices and poor red light (>600 nm) absorbance. Some problems of photosystem II, oxygen evolving part of natural photosynthesis, such as demanding isolation process and D1 photo-damage can also be solved by utilizing BiVO4 as the oxygen evolving part. Preceding research has not suggested any protein-inorganic-hybrid Z-scheme composed of both materials from natural photosynthesis and artificial photosynthesis. In this study, to realize this Z-schematic electron transfer, diffusion step of electron carrier, which usually degrades natural photosynthesis efficiency, was eliminated. Instead, BiVO4 and Pt-photosystem I were all linked together by the mediator gold. Synthesized all-solid-state hybrid materials show enhanced hydrogen evolution ability directly from water when illuminated with visible light.

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TWO-STEP THERMOCHEMICAL CYCLES FOR HYDROGEN PRODUCTION WITH DISH TYPE SOLAR THERMAL SYSTEM (접시형 태양열 집광 시스템을 이용한 열화학 사이클의 수소생산)

  • Kwon, Hae-Sung;Oh, Sang-June;Seo, Tae-Beom
    • 한국태양에너지학회:학술대회논문집
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    • 2011.11a
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    • pp.169-176
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    • 2011
  • The two-step water splitting thermochemical cycle is composed of the T-R (Thermal Reduction)and W-D (Water Decomposition)steps. The mechanism of this cycle is oxidation-reduction, which produces hydrogen. The reaction temperature necessary for this thermochemical cycle can be achieved by a dish-type solar thermal collector (Inha University, Korea). The purpose of this study is to validate a water splitting device in the field. The device is studied and fabricated by Kodama et al (2010, 2011). The validation results show that the foam device, when loaded with $NiFe_2O_4/m-ZrO_2$powder, was successfully achieved hydrogen production with 9 (10 with a Xe-light solar simulator, 2009, Kodama et al.) repeated cycles under field conditions. Two foam device used in this study were tested for validation before an experiment was performed. The lab scale ferrite-conversion rate was in the range of 24~76%. Two foam devices were designed to for structural stability in this study. In the results of the experiments, the hydrogen percentage of the weight of each foam device was 7.194 and $9.954{\mu}mol\;g^{-1}$ onaverage, and the conversion rates 4.49~29.97 and 2.55~58.83%, respectively.

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Hydrogen Production with High Temperature Solar Heat Thermochemical Cycle Using Dual-zone Reactor and CeO2/ZrO2 Foam Device (Dual-zone reactor와 CeO2/ZrO2 Foam Device를 이용한 고온 태양열 열화학 싸이클의 수소 생산)

  • Cho, Ji-Hyun;Seo, Tae-Beom
    • Journal of the Korean Solar Energy Society
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    • v.37 no.5
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    • pp.27-37
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    • 2017
  • In this study, an artificial solar simulator composed of a 2.5 kW Xe-Arc lamp and mirror reflector was used to carry out the solar thermal two step thermochemical water decomposition cycle which can produce high efficiency continuous hydrogen production. Through various operating conditions, the change of hydrogen production due to the possibility of a dual-zone reactor and heat recovery were experimentally analyzed. Based on the reaction temperature of Thermal-Reduction step and Water-Decomposition step at $1,400^{\circ}C$ and $1,000^{\circ}C$ respectively, the hydrogen production decreased by 23.2% under the power off condition, and as a result of experiments using heat recovery technology, the hydrogen production increased by 33.8%. Therefore, when a thermochemical two-step water decomposition cycle is conducted using a dual-zone reactor with heat recovery, it is expected that the cycle can be operated twice over a certain period of time and the hydrogen production amount is increased by at least 53.5% compared to a single reactor.

TWO-STEP THERMOCHEMICAL CYCLES FOR HYDROGEN PRODUCTION WITH DISH TYPE SOLAR THERMAL SYSTEM and $CeO_2/NiFe_2O_4$ (접시형 태양열 집광 시스템과 산화세륨 및 페라이트산화물을 이용한 열화학 사이클의 수소생산)

  • Kwon, Hae-Sung;Oh, Sang-June;Seo, Tae-Beom
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.113-119
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    • 2012
  • The two-step water splitting thermochemical cycle is composed of the T-R (Thermal Reduction) and W-D (Water Decomposition) steps. The mechanism of this cycle is oxidation-reduction, which produces hydrogen. The reaction temperature necessary for this thermochemical cycle can be achieved by a dish-type solar thermal collector (Inha University, Korea). The purpose of this study is to validate a water splitting device in the field. The device is studied and fabricated by Kodama et al (2010, 2011). The validation results show that the foam device, when loaded with $CeO_2$ powder, was successfully achieved hydrogen production under field conditions. Through this experiment, we can analyze the characteristics of the catalyst and able to determine which is more advantageous thing to produce hydrogen compared with previous experiment that used ferrite-device.

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The photocatalytic water splitting into $H_2$ and $O_2$ mimicking a Z-scheme mechanism (광합성을 모사한 광촉매 물분해 수소 제조)

  • Jeon, Myung-Seok;Hong, Joon-Gi;Chun, Young-Gab;Choi, Ho-Suk
    • Journal of the Korean Solar Energy Society
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    • v.23 no.4
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    • pp.29-35
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    • 2003
  • We studied the water splitting into $H_2$ and $O_2$ using two different semiconductor photo catalysts and redox mediator, mimicking the Z-scheme mechanism of the photosynthesis, $H_2$ evolution took place on a Pt-$SrTiO_2$ (Cr-Ta doped) photocatalyst using $I^-$ electron donor under the visible light irradiation. The Pt-$WO_3$ photocatalyst showed an excellent activity of the $O_2$ evolution using $IO_3^-$ electron acceptor under visible light. $H_2$ and $O_2$ gases evolved in the stoichiometric ratio($H_2/O_2$=2) under visible light using a mixture of the Pt-$WO_3$ and Pt-$SrTiO_3$ (Cr-Ta doped) suspended in NaI aqueous solution. We proposed a two-step photo-excitation mechanism using redox mediator under the visible irradiation.