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Researchers Show Mechanism for Catalyst Supported Hydrogen Release in Metal Hydride Storage Systems

16 June 2008

An international research team led by Swedish Professor Rajeev Ahuja, Uppsala University, has demonstrated an atomistic mechanism of hydrogen release in magnesium hydride (MgH2) nanoparticles—a potential on-board hydrogen storage material. The findings have been published in the online edition of Proceedings of the National Academy of Science (PNAS).

Metal hydrides are one of the areas of focus for next-generation hydrogen storage technologies. Magnesium may absorb up to 7.7 weight per cent of hydrogen, and has commonly been studied for this purpose, especially since faster loading and unloading of hydrogen can be accomplished by adding catalysts such as iron and nickel particles.

It has been speculated that the catalysts act as shuttles, helping to transport hydrogen out of the material. With the help of computer simulations of magnesium clusters at the quantum mechanical level, the Uppsala researchers and their colleagues showed in atomic scale how this happens and why only a small amount of catalysts are necessary to improve the hydrogen release.

The team used first-principles calculations based on density functional theory to develop to show that the transition metal atoms Ti, V, Fe, and Ni not only lower desorption energies significantly but also continue to attract at least four hydrogen atoms even when the total hydrogen content of the cluster decreases.

In particular, they found that Fe migrates from the surface sites to the interior sites during the dehydrogenation process, releasing more hydrogen as it diffuses. They suggested that this diffusion mechanism may account for the fact that a small amount of catalyst is sufficient to improve the kinetics of MgH2. The adsorption/desorption kinetics of metal hydrides are typically too slow. Improving the kinetics is essential for the use of this material for hydrogen storage in fuel-cell applications.

The simulations were performed at Uppsala University’s Multidisciplinary Center for Advanced Computational Science (UPPMAX).

We expect the findings to aid further technical improvements of magnesium-based hydrogen storage materials, as well as other related light metal hydrides.

—Professor Raajev Ahuja

In the US, the Department of Energy’s Metal Hydride Center of Excellence (MHCoE) has been researching, developing and validating reversible on-board metal hydride storage materials and systems that meet the 2010 DOE system targets for hydrogen storage, with a credible path forward for meeting the 2015 DOE storage targets.

As part of that work since its inception in FY2005, the MHCoE has been evaluating materials with a focus on five primary performance criteria:

  • The material’s hydrogen storage gravimetric density should be at least 5 weight percent, with a clear potential for much more;

  • The material should be at least 50% reversible after 3 cycles;

  • The material should release its H2 at temperatures below 350 °C;

  • The material’s non-H2 volatilization products should not exceed 1000 ppm for a single thermal cycle; and

  • The material should release and reabsorb H2 in less than 24 hrs.

The MHCoE has so far investigated 51 materials systems across all its materials project areas (destabilized hydrides, complex anionic materials, amide/imide hydrogen storage, and alane). Of these 51 materials, 24 were down-selected, removing them from further study; 27 have satisfied the 5 performance metrics and are being studied further.

Of the hydride materials selected for ongoing work, MHCoE is supporting work on projects with an MgH2-based material, including a catalyst study of LiBH4/MgH2 by Intematix and SNL to increase kinetic performance.

The DOE center is also supporting work on LiBH4/MgH2 to explore the use of nanoconfinement (HRL, Caltech, UTRC, NIST) to increase kinetic performance and a study by Stanford to gain a deeper understanding of the influence of morphology on kinetics.

LiBH4/MgH2 material has shown a reversible wt% hydrogen of 8-10% with the use of a catalyst, but also slow kinetics. The theoretical reversible wt% without catalyst is 11.6% (Another, non-DOE supported material used as a reference point, MgH2/Ninano described by N. Hanada, T. Ichikawa, and H. Fujii in J. Phys. Chem. B, 109, 7188, showed reversible wt% H2 of 6.5% with catalyst, and moderate kinetics. Theoretical reversible wt% without catalyst was 7.6%.)

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June 16, 2008 in Hydrogen Storage | Permalink | Comments (10) | TrackBack (0)

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if all the pork barrel funding that has been wasted on hydrogen and fuel cells for vehicular applications had instead been spent on improving Li-ion battery chemistry and scaling up algae for biodiesel we would all be driving Prii with 100-mile all-electric range and algae-fueled Golf TDIs. instead we are stuck with the same old same old, boffins in their lab coats proclaiming "Gee! we've improved this totally economically unviable process by 1%, isn't that fantastic!". what a waste of research funding and scientific expertise.

Some very influential behind the scenes player has made the decision that hydrogen is the final destination in the future of fuel technology. The items that you mention in your post above are only interim solutions that will eventually be discarded in the far future like the buggy wipe.

Who is that person? ….GWB? ….. Na, It can’t be him, could it?

You just don't get it. Look at all the potential. Not only do these people realize that hydrogen is the most plentiful material in the universe but cold fusion will soon be developed and we can all have nuclear powered Hummers. In an accident, occupants of a hydrogen powered auto will likely be flash frozen making the trip to hospital essentially instantaneous (if they are carefully wrapped like fine china). Parking? Just add a giant "air" bag on the roof and tie your car to a hydrant. It's enough to make me believe in conspiracies. Or wait, maybe if you inhale hydrogen you sound like Donald duck and think like Goofy.

Hydrogen and fuel-hydrogen are different. On the earth, hydrogen must be torn out of water, natural gas or oil at high energy cost and low efficiency. No matter when it is said, the statement, that fusion power will be available in fifty years, is true. Charging batteries in cars is far more efficient than making hydrogen with the electricity. Fuel cells are still very expensive as are large Li-Ion batteries, but the batteries are far less expensive. Serial-plug-in-hybrids are the only affordable answer to the fuel problems of personal cars...HG...

If the Dummicrats had continued to fund the Democrat's own Clinton Administration's obligation for ITER, it would have been built by now. ITER is the LAST fusion experiment before building commercial plants.

We would be designing the first own commerccial power Fusion plant today, if they hadn't been greedy and incapable of following. They didn't, the Dummy Indians were too interested in earmarks for their districts, to pay attention to their own Chief.

ITER I died, and had to be painstakeingly re-created, after pissing off all the countries who had spent billions already. It delayed Fusion power by 10-15 years.

Then the dopey Dems took power in Congress, and did it again! This time to a Republican president, who had got ITER II going once again. Pissing off the the other nations, once again, the EU, Russia, India, China, Japan Korea, who have spent billions once again.

Their word and promises have the constancy, and spine,+ of cooked spaghetti. All for a little local "earmarked" corruption.

As a noted proverb says: "Lead. Or follow. Or get the hell out of the way."

These spineless, wimpy Jackasses will do neither.

Even if a commercial fusion reactor design were available yesterday it would still take decades to make any significant impact on our energy situation.
If the Bushies hadn't dumped the PNGV for purely ideological reasons (if Clinton liked it we must be against it) The big three would be thriving and the Japanese would be playing catch up. Instead we have had these silly subsidies for a mythical hydrogen economy that the right wing media has propagandized the masses into believing its just around the corner.

This is a very important research, since H2 adsorption allows large amount of H2 storage at lower pressures that will make H2 storage compact and cost-effective.

H2 is the simplest and most efficient fuel that can be made from renewable energy anywhere using very simple equipment. Even the synthesis of methane (CH4) will require more steps, a carbon source, and much less efficient than H2. Future societies, whether on earth, the moon or Mars, will need a large amount of stored synthetic fuel for backing up direct solar and wind electricity. Cellulosic biomass will be too valuable as a source of raw material for the organic chemical industry and plastic industry, when petroleum will be all gone.

I hate these Democrats. Wish they never existed. They are responsible for me having to scroll past pagefuls of rants from stas peterson.

Hydrogen absorption in metal hydride systems is potentially interesting even without the use of hydrogen as a fuel. Cycling the hydrogen between gas and chemically bound forms can be used as a way to store thermal energy. This could be useful in conjunction with concentrating solar collectors.

I WOULD LIKE TO KNOW THE PROCEDURE OF THE INTERCALATION OF LI- WITH MGH2

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