Cycling and thermal stability of nanostructured MgH2–Cr2O3 composite for hydrogen storage

Dehouche, Zahir; Klassen, Thomas; Oelerich, W.; Goyette, J.; Bose, T. K.; Schulz, Robert

doi:10.1016/s0925-8388(02)00784-3

Cited by 191 publications

(89 citation statements)

References 31 publications

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“…These are similar to literature results of discharging MgH 2 with different oxide catalysts at 300 °C into vacuum [38]. The reduction in discharge kinetics over four cycles can potentially be attributed to the exposure to high temperatures which leads to significant coarsening of the microstructure resulting in a slow-down of kinetics [40]. The authors went on to show that oxides have a larger impact on desorption of MgH 2 that absorption; therefore, the desorption cycle is more sensitive to catalyst deterioration [40].…”

Section: Decomposition Behavior Of As-milled Modified Materialssupporting

confidence: 89%

“…The reduction in discharge kinetics over four cycles can potentially be attributed to the exposure to high temperatures which leads to significant coarsening of the microstructure resulting in a slow-down of kinetics [40]. The authors went on to show that oxides have a larger impact on desorption of MgH 2 that absorption; therefore, the desorption cycle is more sensitive to catalyst deterioration [40]. Klassan et al discussed that transition metal oxides showed more improvement on sorption kinetics than their pure metal counterparts [38], indicating that once the oxides are reduced during cycling, they lose their effectiveness [39].…”

Section: Decomposition Behavior Of As-milled Modified Materialsmentioning

confidence: 99%

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Affects of Mechanical Milling and Metal Oxide Additives on Sorption Kinetics of 1:1 LiNH2/MgH2 Mixture

2011

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Abstract:The destabilized complex hydride system composed of LiNH 2 :MgH 2 (1:1 molar ratio) is one of the leading candidates of hydrogen storage with a reversible hydrogen storage capacity of 8.1 wt%. A low sorption enthalpy of ~32 kJ/mole H 2 was first predicted by Alapati et al. utilizing first principle density function theory (DFT) calculations and has been subsequently confirmed empirically by Lu et al. through differential thermal analysis (DTA). This enthalpy suggests that favorable sorption kinetics should be obtainable at temperatures in the range of 160 °C to 200 °C. Preliminary experiments reported in the literature indicate that sorption kinetics are substantially lower than expected in this temperature range despite favorable thermodynamics. Systematic isothermal and isobaric sorption experiments were performed using a Sievert's apparatus to form a baseline data set by which to compare kinetic results over the pressure and temperature range anticipated for use of this material as a hydrogen storage media. Various material preparation methods and compositional modifications were performed in attempts to increase the kinetics while lowering the sorption temperatures. This paper outlines the results of these systematic tests and describes a number of beneficial additions which influence kinetics as well as NH 3 formation.

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Section: Decomposition Behavior Of As-milled Modified Materialssupporting

confidence: 89%

Section: Decomposition Behavior Of As-milled Modified Materialsmentioning

confidence: 99%

Affects of Mechanical Milling and Metal Oxide Additives on Sorption Kinetics of 1:1 LiNH2/MgH2 Mixture

2011

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“…A distinct improvement of the sorption kinetics is obtained by the addition of chromium oxide catalyst (Dehouche et al, 2002). In Pranzas et al (2006), SANS/USANS curves of MgH 2 samples after addition of 10 wt% of normal chromium oxide (micro-Cr 2 O 3 ) and commercially available nanoparticles (nano-Cr 2 O 3 ) after 200 h of milling using steel vials and balls were presented with a first interpretation of the scattering curves.…”

Section: Resultsmentioning

confidence: 99%

Small-angle scattering investigations of magnesium hydride used as a hydrogen storage material

Pranzas¹,

Dornheim²,

Bösenberg³

et al. 2007

J Appl Cryst

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In this work, high‐energy ball‐milled magnesium hydride samples used for hydrogen storage are investigated using small‐ and ultra‐small‐angle neutron scattering (SANS) as well as small‐angle X‐ray scattering (SAXS). Size distributions of inhomogeneities with dimensions from 10 Å up to more than 10 µm, corresponding to crystallite and particle sizes obtained by X‐ray diffraction and electron microscopy, are determined as a function of milling time, milling tool material and added metal oxide catalysts in order to study the influence of the microstructure on the sorption kinetics. Significant changes of the volume fraction distributions are found for samples containing the catalyst chromium oxide, particularly when the catalyst particles are nanometre‐sized. Cr2O3 is an effective agent for breaking up particles during the milling process. The comparison of SANS and SAXS curves give some of the first information about the distribution of hydrogen‐containing structures. Using anomalous small‐angle X‐ray scattering, an energy‐dependent scattering is found for an MgHx sample with 1 mol% Fe2O3. From the separated scattering curve a size distribution of hard spheres is obtained with a size range which is expected for crystallite and particle sizes of the Fe2O3 catalyst. Chemical shifts in the absorption spectra give information about the stability of the metal oxide catalysts during the milling process.

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“…Recently, Kanoya et al have investigated H-storage properties of some ball milled Mg with a small amount of nano-sized metals (Ni and Fe) as a catalyst. 79) Their results indicated that Mg- [80][81][82][83] The composites prepared by ball milling for 100 h with 0.2 mol% Nb 2 O 5 absorbed 7 mass% of hydrogen within 60 s and desorbed within 130 s at 300 C. 83) In our group, it has been reported that Pd-coated nanostructured Mg films prepared by a RF sputtering method absorb $5 mass% at 100 C under hydrogen atmosphere of 0.1 MPa and completely desorb below 100 C in vacuum. This confirms that MgH 2 is applicable for practical use if we can modify bulk MgH 2 into suitable nano-structure.…”

Section: Hydrogen Storage Properties Of Magnesium Based Materialsmentioning

confidence: 99%

Composite Materials based on Light Elements for Hydrogen Storage

et al. 2005

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In this paper, we review our recent experimental results on hydrogen storage properties of light elements Li, C and Mg based nanocomposite materials. The results are summarized as follows: In the Li-N-H system, such as the ball milled 1:1 mixture of Li amide and Li hydride containing a small amount of TiCl 3 (1 mol%), a large amount of hydrogen ($6 mass%) is absorbed and desorbed in the temperature range from 150 to 250 C with good reversibility and high reaction rate. Furthermore, in the ball milled mixture of 3Mg(NH 2 ) 2 and 8LiH, $7 mass% of hydrogen is reversibly stored in the temperature from 140 to 220 C, indicating one of the suitable hydrogen storage materials. In graphite containing a small amount of nanometer sized Fe ($2 at.%), a large amount of hydrogen ($7 mass%) is chemisorbed by ball milling for 80 h under less than 1 MPa of H 2 -gas pressure. However, the chemisorbed hydrogen capacity decreases with increase in the milling pressure for the 80 h ball milled graphite (down to $4:1 mass% at 6 MPa), while the physisorbed hydrogen capacity in graphite increases with increase in the milling pressure, reaching up to 0:5$1:0 mass% at 6 MPa. Unfortunately, the desorption temperature of chemisorbed hydrogen is higher than 300 C. Therefore, some break-through is necessary for the development of carbon-based materials as one of the hydrogen storage systems. On the other hand, some nano-composite Mg catalyzed by Ni nano-particle or Nb oxide reveals superior reversible hydrogen storage properties: $6:5 mass% of hydrogen is reversibly stored in the temperature range from 150 to 250 C. Especially, the Nb metals uniformly dispersed in nanometer scale on the surface of MgH 2 , which was produced by reduction of Nb 2 O 5 , is the best catalyst we have studied so far. Thus, it seems that some Mg nano-composites catalyzed by nano-particles of d-electron transition metals is acceptable for practical applications.

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Cycling and thermal stability of nanostructured MgH2–Cr2O3 composite for hydrogen storage

Cited by 191 publications

References 31 publications

Affects of Mechanical Milling and Metal Oxide Additives on Sorption Kinetics of 1:1 LiNH2/MgH2 Mixture

Affects of Mechanical Milling and Metal Oxide Additives on Sorption Kinetics of 1:1 LiNH2/MgH2 Mixture

Small-angle scattering investigations of magnesium hydride used as a hydrogen storage material

Composite Materials based on Light Elements for Hydrogen Storage

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