Kinetic and dynamic aspects of rechargeable metal hydrides

Goodell, P.D.; Sandrock, G.; Huston, E.L.

doi:10.1016/0022-5088(80)90352-5

Cited by 121 publications

(20 citation statements)

References 7 publications

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“…Taking the absorption of hydrogen (which is usually slower than the desorption at a given temperature) as an example, the following steps can be discerned: For a mathematical analysis of the different steps we refer to the literature. [63][64][65] Hydrogen physisorption (step 1) is a fast process, and hence generally not rate-limiting, and steps 3 and 5 are also rarely rate-limiting, except when nucleation barriers play an important role, at the initial stage of the conversion. Typically the rate-limiting step is either the dissociation of hydrogen at the surface (which depends on the surface concentration and hence indirectly on the physisorption parameters), or the diffusion of hydrogen through the hydride to the metal/ hydride interface, or a combination of both.…”

Section: Impact On Kinetics and Reversibilitymentioning

confidence: 99%

Nanosizing and Nanoconfinement: New Strategies Towards Meeting Hydrogen Storage Goals

2010

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Hydrogen is expected to play an important role as an energy carrier in a future, more sustainable society. However, its compact, efficient, and safe storage is an unresolved issue. One of the main options is solid-state storage in hydrides. Unfortunately, no binary metal hydride satisfies all requirements regarding storage density and hydrogen release and uptake. Increasingly complex hydride systems are investigated, but high thermodynamic stabilities as well as slow kinetics and poor reversibility are important barriers for practical application. Nanostructuring by ball-milling is an established method to reduce crystallite sizes and increase reaction rates. Since five years attention has also turned to alternative preparation techniques that enable particle sizes below 10 nanometers and are often used in conjunction with porous supports or scaffolds. In this Review we discuss the large impact of nanosizing and -confinement on the hydrogen sorption properties of metal hydrides. We illustrate possible preparation strategies, provide insight into the reasons for changes in kinetics, reversibility and thermodynamics, and highlight important progress in this field. All in all we provide the reader with a clear view of how nanosizing and -confinement can beneficially affect the hydrogen sorption properties of the most prominent materials that are currently considered for solid-state hydrogen storage.

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Section: Impact On Kinetics and Reversibilitymentioning

confidence: 99%

Nanosizing and Nanoconfinement: New Strategies Towards Meeting Hydrogen Storage Goals

2010

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“…TiFe exhibits two plateaus, a lower plateau (alpha-beta) from 0.1-0.5 HIM and an upper plateau (beta-gamma) from about 0.55 -0.85 H/M. The lower plateau is vety stable with cycling, but the upper plateau increases in pressure [29]. In addition, TiFe does not readily activate at room temperature.…”

Section: Hydrogen Storage Materials Selection and Propertiesmentioning

confidence: 98%

Compact fuel cell system utilizing a combination of hydrogen storage materials for optimized performance.

Chan¹,

Dedrick²,

Gross³

et al. 2004

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Abstractn entirely new class of light-weight reversible hydrides was recently discovered (the Tidoped alanates)[lI. These NaAIH,-based materials have demonstrated reversible hydrogen storage capacities of up to 5 wt%, nearly 4 times the gravimetrically density of commercial metal hydrides. For this reason, they have been considered a breakthrough for hydrogen storage in fuel cell vehicles. This project is the first to publish the use of alanates for the generation of electrical power and the first demonstration of a hydride-fueled elevatedtemperature PEM Fuel Cell. Because the kinetics of hydrogen uptake and release by the alanate improves with elevated temperatures, novel concepts were tested for the purpose of developing a highly efficient stand-alone power system. A major focus of this work was on the modeling, design, construction and testing of an integrated fuel cell stack and hydrogen storage system that eliminates the need of complicated heat transfer systems and media. After extensive modeling efforts, a proof-of-concept system was built that employs an integrated fuel cell stack and hydride beds that balancing the generation of fuel cell waste heat with the endothermic release of hydrogen from the alanates. Our demonstration unit was capable of greater than one hour of operation on a single charge of hydrogen from the integrated 173 gram alanate bed. In addition, composite hydride materials with synergistic reaction heats were evaluated and tested to enhance the operational performance of the alanates. The composites provide a unique opportunity to utilize the heat produced from hydriding classic metal hydrides to improve both absorption and desorption rates of the alanates. A particular focus of the mixed storage materials work was to balance the thermodynamics and kinetics of the hydrides for start-up conditions. Modeling of the sorption properties proved invaluable in evaluating the optimum composition of hydrides. The modeling efforts were followed by full validation by experimental measurements. This project successfully completed the proof-of-concept goals and generated a powerful set of tools for optimizing the complete power-generation system. It has also created a new direction for hydrogen power generation as well the potential for new R&D based on this work.

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“…[10] Work on the hydrogen absorbing-desorbing cycle durability by using H 2 with 300 ppm O 2 , H 2 O or CO has revealed that the presence of CO has the severest effect on hydrogen storage ability. [11] Systematic investigations on the cyclic durability of Ca-Mg-Ni and Ti-V alloys with pure H 2 and with CO-contaminated H 2 indicate that the hydrogen storage capacities of the alloys decrease seriously with increasing CO concentration. Surprisingly, though, the crystal structures of bulk alloys before and after absorbing-desorbing cycles remain almost unchanged.…”

Section: Introductionmentioning

confidence: 99%

CO Adsorption on a LaNi₅ Hydrogen Storage Alloy Surface: A Theoretical Investigation

et al. 2008

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Density functional theory calculations are carried out to study CO adsorption on the (001) surface of a LaNi(5) hydrogen storage alloy. At low coverages, CO favors adsorption on Ni-Ni bridge sites. With an increase in CO coverage, the decrease in the adsorption energy is much larger for Ni-Ni-CO bridge adsorption than that for Ni-CO on-top adsorption. Thus, the latter sites in the relatively stable adsorption structure are preferentially utilized at high CO coverages. The nature of the bonding between CO and the LaNi(5) (001) surface is analyzed in detail.

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Kinetic and dynamic aspects of rechargeable metal hydrides

Cited by 121 publications

References 7 publications

Nanosizing and Nanoconfinement: New Strategies Towards Meeting Hydrogen Storage Goals

Nanosizing and Nanoconfinement: New Strategies Towards Meeting Hydrogen Storage Goals

Compact fuel cell system utilizing a combination of hydrogen storage materials for optimized performance.

CO Adsorption on a LaNi₅ Hydrogen Storage Alloy Surface: A Theoretical Investigation

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Kinetic and dynamic aspects of rechargeable metal hydrides

Cited by 121 publications

References 7 publications

Nanosizing and Nanoconfinement: New Strategies Towards Meeting Hydrogen Storage Goals

Nanosizing and Nanoconfinement: New Strategies Towards Meeting Hydrogen Storage Goals

Compact fuel cell system utilizing a combination of hydrogen storage materials for optimized performance.

CO Adsorption on a LaNi5 Hydrogen Storage Alloy Surface: A Theoretical Investigation

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CO Adsorption on a LaNi₅ Hydrogen Storage Alloy Surface: A Theoretical Investigation