Enhancement of O2-releasing step with Fe2O3 in the water splitting by MnFe2O4–Na2CO3 system

Kaneko, Hiroshi; Hosokawa, Y; Gokon, Nobuyuki; Kojima, Noboru; Hasegawa, Noriko; Kitamura, Mitsunobu; Tamaura, Yutaka

doi:10.1016/s0022-3697(01)00034-8

Cited by 24 publications

(24 citation statements)

References 11 publications

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“…However, their cycle was not closed due to the use of sacrificial Fe 2 O 3 to extract Na þ from sodium manganese iron oxide produced in the hydrogen evolution step (22). Sodium sources other than Na 2 CO 3 , such as NaOH, have also been employed to facilitate the oxidation of Mn 2þ to Mn 3þ in the water splitting step (23).…”

Section: Resultsmentioning

confidence: 99%

Low-temperature, manganese oxide-based, thermochemical water splitting cycle

Bhawe

Davis

2012

Proc. Natl. Acad. Sci. U.S.A.

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Thermochemical cycles that split water into stoichiometric amounts of hydrogen and oxygen below 1,000°C, and do not involve toxic or corrosive intermediates, are highly desirable because they can convert heat into chemical energy in the form of hydrogen. We report a manganese-based thermochemical cycle with a highest operating temperature of 850°C that is completely recyclable and does not involve toxic or corrosive components. The thermochemical cycle utilizes redox reactions of Mn(II)/Mn(III) oxides. The shuttling of Na þ into and out of the manganese oxides in the hydrogen and oxygen evolution steps, respectively, provides the key thermodynamic driving forces and allows for the cycle to be closed at temperatures below 1,000°C. The production of hydrogen and oxygen is fully reproducible for at least five cycles.hydrogen production | Na + extraction | multistep cycle T hermochemical production of hydrogen and oxygen from water involves a series of chemical reactions that convert water into stoichiometric amounts of hydrogen and oxygen using heat as the only energy source. Thermochemical water splitting is of interest because it directly converts thermal energy into stored chemical energy (hydrogen and oxygen). Research on thermochemical water splitting cycles largely began in the 1960s and 1970s and involved nuclear reactors (1, 2) and solar collectors (3) as the energy sources. Numerous reviews of the thermochemical cycles proposed and experimentally investigated are available, e.g., (4). A large number of thermochemical cycles for splitting water has been proposed, and generally can be grouped into two broad categories: high-temperature two-step processes (5, 6) and lowtemperature multistep processes (7,8). One of us (M.E.D.) has conducted previous research on low-temperature multistep processes in the 1970s (9).Low-temperature multistep processes, typically with the a highest operating temperature below 1,000°C, allow for the use of a broader spectrum of heat sources, such as heat from nuclear power plants, and hence have attracted considerable attention. The majority of existing low-temperature processes produces intermediates that can be complex, corrosive halide mixtures. One of these processes, the sulfur-iodine cycle, has been studied extensively, and even piloted for implementation (8). This process produces strongly acidic mixtures of sulfuric and iodic acids that create significant corrosion issues, but requires only one high-temperature step at ca. 850°C. Two-step processes typically involve simpler reactions and intermediates, e.g., solid metal oxides, than the low-temperature multistep cycles. However, the temperatures required to close these types of cycles are well above 1,000°C. Because of the requirement of high-temperature heat sources, these types of cycles have been investigated for use with solar concentrators (10, 11). These cycles typically consist of one step that involves the oxidation of a metal [such as zinc (12)] or a metal oxide [such as iron (II) oxide (6, 13)] by water to produce...

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Section: Resultsmentioning

confidence: 99%

Low-temperature, manganese oxide-based, thermochemical water splitting cycle

Bhawe

Davis

2012

Proc. Natl. Acad. Sci. U.S.A.

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“…Modification involving the introduction of Fe 2 O 3 as a sacrificial agent has been proposed, but the use of Fe 2 O 3 does not close the cycle either (12).…”

Section: Low-temperature Multistep Cyclesmentioning

confidence: 99%

Solar thermochemical splitting of water to generate hydrogen

Rao

Dey

2017

Proc. Natl. Acad. Sci. U.S.A.

126

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Solar photochemical means of splitting water (artificial photosynthesis) to generate hydrogen is emerging as a viable process. The solar thermochemical route also promises to be an attractive means of achieving this objective. In this paper we present different types of thermochemical cycles that one can use for the purpose. These include the low-temperature multistep process as well as the high-temperature two-step process. It is noteworthy that the multistep process based on the Mn(II)/Mn(III) oxide system can be carried out at 700°C or 750°C. The two-step process has been achieved at 1,300°C/900°C by using yttrium-based rare earth manganites. It seems possible to render this high-temperature process as an isothermal process. Thermodynamics and kinetics of H 2 O splitting are largely controlled by the inherent redox properties of the materials. Interestingly, under the conditions of H 2 O splitting in the high-temperature process CO 2 can also be decomposed to CO, providing a feasible method for generating the industrially important syngas (CO+H 2 ). Although carbonate formation can be addressed as a hurdle during CO 2 splitting, the problem can be avoided by a suitable choice of experimental conditions. The choice of the solar reactor holds the key for the commercialization of thermochemical fuel production. The impact of global climate change as well as the likely shortage of fossil fuels demand harvesting of energy using renewable sources. Although solar energy captured by the Earth in an hour is expected to satisfy the energy demand of the world for a year, the high energy density and nonpolluting end product renders hydrogen a viable alternative to fossil fuels (1). In this context, conversion of solar power to H 2 and synfuels with the utilization of renewable H 2 O and CO 2 seems to be a sound option. Artificial photosynthesis and photovoltaic-powered electrolysis of water are promising approaches, although their implementation is somewhat restricted because of the low solar-tofuel conversion efficiency (η solar-to-fuel ) of <5% and <15%, respectively (2, 3). The other strategy would be a solarthermochemical process that provides a high theoretical efficiency and enables large-scale production of H 2 by using the entire solar spectrum (4). Research in thermochemical splitting of H 2 O made a beginning in the early 1980s (5, 6) and several thermochemical cycles have been examined. Thermochemical methods come under two main categories, the low-temperature multistep processes and the high-temperature two-step processes. The two-step process involving the thermal decomposition of metal oxides followed by reoxidation by reacting with H 2 O to yield H 2 is an attractive and viable process that can be rendered to become an isothermal process. Thermochemical splitting of H 2 O at low temperatures (<1,000°C) is accomplished by a minimum of three steps as dictated by thermodynamic energy constraints (7,8). In this paper we present the highlights of recent investigations of H 2 O splitting by the low-temperature m...

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“…2. The schematic outline of two-step water spliting system with Zn-ferrite /Zn, Fe3O4 system [25] The solar decomposition of the Zn ferrite commenced above 1500 K and its decomposition ratio at 1750 K was evaluated to be 40% form the lattice constant measurement and chemical analysis. The solar decomposition of Zn ferrite can be readily with increasing temperature.…”

Section: Zinc Ferrite Catalyst In the Hydrogen Production From The Dementioning

confidence: 99%

“…These results encourage further investigation for solar operation to enhance the solar decomposition ratio of the Zn ferrite. The thermochemical cycles for H 2 production with Zn ferrite, Fe 2 O 3 system will be realized by the enhancement of solar decomposition of the Zn ferrite [25].…”

Section: Zinc Ferrite Catalyst In the Hydrogen Production From The Dementioning

confidence: 99%

Use of Specific Properties of Zinc Ferrite in Innovative Technologies

Kmita¹,

Pribulová²,

Holtzer³

et al. 2016

Archives of Metallurgy and Materials

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Zinc ferrite ZnFe2O4 both in the micro and nano scale is widely used in various fields. The article discusses the structure of this compound and its properties in the nanoscale, which is clearly different from those which the ferrite shows in the microscale. The properties of dust generated electric arc furnace, which can contain up to 40% zinc, substantially in the form of ZnFe2O4 are disscused here. Specific properties (electric, magnetic, thermal) of zinc ferrite nanoparticles determine the very wide possibilities of their use, inter alia as catalysts, absorbents, gas sensors, and a tool to combat cancer.

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Enhancement of O2-releasing step with Fe2O3 in the water splitting by MnFe2O4–Na2CO3 system

Cited by 24 publications

References 11 publications

Low-temperature, manganese oxide-based, thermochemical water splitting cycle

Low-temperature, manganese oxide-based, thermochemical water splitting cycle

Solar thermochemical splitting of water to generate hydrogen

Use of Specific Properties of Zinc Ferrite in Innovative Technologies

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