Structural and electrochemical characteristics of a lamellar sodium manganese oxide synthesized via a sol-gel process

Goff, Philippe Le; Baffier, N.; Bach, S.; Pereira-Ramos, J.P.; Messina, R.

doi:10.1016/0167-2738(93)90397-l

Cited by 63 publications

(39 citation statements)

References 13 publications

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“…2, steps 1 and 2) contains α-NaMnO 2 and a hydrated product α-Na 0.7 MnO 2.14 [ Fig. 4, i; α-NaMnO 2 can form α-Na 0.7 MnO 2.14 when exposed to water (16)]. Importantly, the XRD pattern of the powder collected after step 1 clearly shows the presence of MnO in addition to the peaks attributed to α-NaMnO 2 and α-Na 0.7 MnO 2.14 ( Fig.…”

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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“…It consists of a water washing [24]. After one hour the reaction is over and leads to the final product Na0.45MnO2.0.6H20.…”

Section: Synthesis the Sol-gel Birnessitementioning

confidence: 99%

Influence of cobalt ions on the electrochemical properties of lamellar manganese oxides

Franger

Bach

Pereira-Ramos

et al. 2000

Ionics

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Abstract. Evaluation of Co-doping on the electrochemical properties of the sol-gel birnessite and the new lithiated manganese oxide Li0.45MnO2+ 5 is reported. For both compounds the synthesis of Co-doped materials via a solution technique is described. We demonstrate the interest of Co-doped structures with the selected content of 0.15 Co per mole of oxide as the optimum composition. In the case of Li0.45Mnl_yCOyO2+ 8, prepared at 300 ~ a mixture of a lamellar phase and a cubic one is identified while the Co-doped birnessite appears as a single phase. A probable substitution of Mn by Co ions explains the better specific capacity of 185 mAh/g found and the excellent stability observed over 40 cycles in the voltage range 4.2-2.0 V.

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“…Sin embargo, ésta no parece ser la situación real, pues las birnesitas que se han obtenido por el método sol-gel han sido sometidas a calcinación hasta 400 °C. Le Goff y col. (22) han propuesto que, en el caso de birnesitas de Na preparadas por el método sol-gel utilizando ácido fumárico como reductor, los sólidos preparados pierden agua hasta unos 400 °C.…”

Section: Análisis Térmicosunclassified

Preparación y caracterización de óxidos de manganeso no estequiométricos

Prieto¹,

Rives²

2000

Bol. Soc. Esp. Ceram. Vidr.

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Se describe la preparación y caracterización fisicoquímica por diversas técnicas (análisis químico elemental, difracción de rayos X, espectroscopía FT-IR, análisis térmico y determinación de superficie específica) de birnesitas de Na, K y Li preparadas por diversos métodos. Asimismo, se han estudiado sus propiedades de cambio iónico, caracterizando las muestras intercambiadas por las mismas técnicas. Se ha encontrado que el intercambio es prácticamente total en el caso del Li, mientras que en el caso de Cu y Mg el porcentaje intercambiado es relativamente bajo. Palabras claves: birnesita, óxidos de Mn, no estequiometría. Preparation and characterization of nonstoichiometric manganese oxidesSynthesis and physicochemical characterization (elemental chemical analysis, powder X-ray diffraction, FT-IR spectroscopy, thermal analysis and specific surface area determination) of Na, K and Li birnessites are described. The ionic exchange abilities of these materials have been studied, and the exchanged samples have been characterized following the same experimental techniques. An almost complete ionic exchange has been observed for Li, while exchange for Cu and Mg is rather low, probably because of ionic radii differences.

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Structural and electrochemical characteristics of a lamellar sodium manganese oxide synthesized via a sol-gel process

Cited by 63 publications

References 13 publications

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

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

Influence of cobalt ions on the electrochemical properties of lamellar manganese oxides

Preparación y caracterización de óxidos de manganeso no estequiométricos

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