The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Alberto J. Quejido - One of the best experts on this subject based on the ideXlab platform.
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Understanding water-splitting thermochemical cycles based on nickel and cobalt Ferrites for hydrogen production
International Journal of Hydrogen Energy, 2019Co-Authors: Naiara B. Goikoetxea, Rocío Fernández-saavedra, M. Belén Gómez-mancebo, Fernando Borlaf, Fernando García-pérez, José Antonio Jiménez, Irene Llorente, Isabel Rucandio, Alberto J. QuejidoAbstract:Abstract Two step water-splitting cycles by using metal Ferrites are considered as a clean and sustainable hydrogen production method, when concentrated solar energy is used to drive the thermochemical reactions. This process involves the reduction at very high temperature of the ferrite, followed by the water reoxidation to the original phase at moderate temperature, with the release of hydrogen. In order to decrease the temperature required to decompose the oxide, mixed Ferrites of the type MFe2O4 with spinel crystal structure have been examined. In this sense, Ferrites with the partial substitution of Co and Ni for Fe appear as successful materials in terms of hydrogen production and cyclability. In this work, commercial Ni and synthetic Co Ferrites have been subjected to two water splitting cycles. The solid products obtained after thermal reduction and water decomposition reactions have been chemically and structurally characterized by WDXRF, XRD, XPS and SEM techniques, in order to get a deeper understanding of the mechanisms controlling the water splitting process. This knowledge contributes to improve the process involved in thermochemical cycles and to understand the lower efficiencies (H2/O2) for Co ferrite thermochemical cycles in comparison with those corresponding to Ni ferrite.
Kwang Deog Jung - One of the best experts on this subject based on the ideXlab platform.
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Water splitting for hydrogen production with Ferrites
Solar Energy, 2007Co-Authors: Sangbum Han, Tae Bum Kang, Oh-shim Joo, Kwang Deog JungAbstract:Abstract The water splitting reaction by a thermo-chemical cycle using Ferrites was investigated for H2 production. In the first step (activation step), Ferrites were thermally reduced at 1200 °C to form an oxygen-deficient ferrite. In the second step (water splitting step), the activated Ferrites were oxidized by water at 800 °C to produce hydrogen. Among the prepared Ferrites, Ni-ferrite was found to be the most suitable for H2 production. NiFe2O4 produced an average of 0.442 cm3/g cycle of H2. The H2 productivity of the Ni-ferrite was much higher than that of the other Ferrites at the same temperature. XRD showed that the crystal structure of NiFe2O4 during the redox reaction was not changed during the repeated cycles, indicating that NiFe2O4 was an excellent material in terms of structural stability and durability.
S V Narasimhan - One of the best experts on this subject based on the ideXlab platform.
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formation of zinc ferrite by solid state reaction and its characterization by xrd and xps
Journal of Materials Science, 2001Co-Authors: Santanu Bera, A A M Prince, S Velmurugan, P S Raghavan, R Gopalan, G Panneerselvam, S V NarasimhanAbstract:A dry mixture of ZnO and α-Fe2O3was annealed at 1200°C; the progress of the formation of the ferrite was monitored by XRD and XPS analyses at different time intervals. The presence of octahedral zinc cation was observed along with the regular tetrahedral Zn in the sample that had undergone 30 minute heat treatment. After three hours of heating, pure normal zinc ferrite was formed. The Zn 2p3/2peak binding energy, intensity and line shape were analyzed extensively to show the diffusion of ZnO and the growth of ferrite at different stages of heat treatment. Analysis of the Fe 2p3/2line-shape supported the substitution of Fe2+by zinc cations during ferrite formation. The binding energy values of the Zn 2p levels for stoichiometric and non-stoichiometric Ferrites were also determined and surface segregation of the zinc was observed by XPS in the non-stoichiometric Ferrites.
Naiara B. Goikoetxea - One of the best experts on this subject based on the ideXlab platform.
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Understanding water-splitting thermochemical cycles based on nickel and cobalt Ferrites for hydrogen production
International Journal of Hydrogen Energy, 2019Co-Authors: Naiara B. Goikoetxea, Rocío Fernández-saavedra, M. Belén Gómez-mancebo, Fernando Borlaf, Fernando García-pérez, José Antonio Jiménez, Irene Llorente, Isabel Rucandio, Alberto J. QuejidoAbstract:Abstract Two step water-splitting cycles by using metal Ferrites are considered as a clean and sustainable hydrogen production method, when concentrated solar energy is used to drive the thermochemical reactions. This process involves the reduction at very high temperature of the ferrite, followed by the water reoxidation to the original phase at moderate temperature, with the release of hydrogen. In order to decrease the temperature required to decompose the oxide, mixed Ferrites of the type MFe2O4 with spinel crystal structure have been examined. In this sense, Ferrites with the partial substitution of Co and Ni for Fe appear as successful materials in terms of hydrogen production and cyclability. In this work, commercial Ni and synthetic Co Ferrites have been subjected to two water splitting cycles. The solid products obtained after thermal reduction and water decomposition reactions have been chemically and structurally characterized by WDXRF, XRD, XPS and SEM techniques, in order to get a deeper understanding of the mechanisms controlling the water splitting process. This knowledge contributes to improve the process involved in thermochemical cycles and to understand the lower efficiencies (H2/O2) for Co ferrite thermochemical cycles in comparison with those corresponding to Ni ferrite.
Sangbum Han - One of the best experts on this subject based on the ideXlab platform.
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Water splitting for hydrogen production with Ferrites
Solar Energy, 2007Co-Authors: Sangbum Han, Tae Bum Kang, Oh-shim Joo, Kwang Deog JungAbstract:Abstract The water splitting reaction by a thermo-chemical cycle using Ferrites was investigated for H2 production. In the first step (activation step), Ferrites were thermally reduced at 1200 °C to form an oxygen-deficient ferrite. In the second step (water splitting step), the activated Ferrites were oxidized by water at 800 °C to produce hydrogen. Among the prepared Ferrites, Ni-ferrite was found to be the most suitable for H2 production. NiFe2O4 produced an average of 0.442 cm3/g cycle of H2. The H2 productivity of the Ni-ferrite was much higher than that of the other Ferrites at the same temperature. XRD showed that the crystal structure of NiFe2O4 during the redox reaction was not changed during the repeated cycles, indicating that NiFe2O4 was an excellent material in terms of structural stability and durability.