• CORRECTION: This story was changed on Jan. 8, 2015, to correct the details of the DOE’s target for hydrogen storage and to remove an error in the image caption about the amount of hydrogen released by the reaction.
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Web Date: January 7, 2015

New Hydrogen Storage Material Can Take The Heat

Alternative Energy: Amine borane compound remains stable at sustained high temperatures
Department: Science & Technology | Collection: Sustainability
News Channels: Materials SCENE, Environmental SCENE, Organic SCENE, JACS In C&EN
Keywords: hydrogen storage, amine borane, fuel cells
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HOLDING HYDROGEN
In the presence of a ruthenium catalyst, bis-BN cyclohexane (left) releases hydrogen at room temperature in about 15 minutes, producing a cage compound as a by-product (right).
Credit: J. Am. Chem. Soc.
Reaction scheme for hydrogen release from bis-BN cyclohexane.
 
HOLDING HYDROGEN
In the presence of a ruthenium catalyst, bis-BN cyclohexane (left) releases hydrogen at room temperature in about 15 minutes, producing a cage compound as a by-product (right).
Credit: J. Am. Chem. Soc.

Hydrogen gas is touted as a possible clean alternative energy source. But without a way to store the gas safely, hydrogen-fuel cells won’t be practical. And for some applications, the stored gas must be stable for long periods of time, sometimes under extreme temperatures. Now, researchers have created an H2 storage molecule that does not decompose even at temperatures up to 150 °C (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja511766p).

Shih-Yuan Liu, an organometallic chemist at Boston College, and his colleagues work on synthesizing amine borane compounds that can store and release H2. Amine boranes have relatively high H2-storage capacities and can release the gas quickly, but generally the compounds aren’t stable at high temperatures.

The researchers synthesized the new compound, a bis-BN cyclohexane in three steps. When dissolved in tetrahydrofuran along with a ruthenium catalyst at room temperature, the compound releases hydrogen in as little as 15 minutes.

The molecule’s storage capacity is 4.7% hydrogen by weight. For use in vehicle fuel cells, the researchers would have to reengineer the compound to increase capacity, Liu says, seeing as the Department of Energy has set a 5.5 wt % target for hydrogen storage systems for 2020. But the compound may be appropriate for other applications, such as in backup generators that would store energy long term in case of a natural disaster, he says.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
Comments
Robert Buntrock (Fri Jan 09 11:17:38 EST 2015)
Details are needed on the preparation of this borane so that it can truly act as a storage device. (I'd look at the JACS paper but I don't have a subscription nor do I want to "burn" one of my free accessions.)
Robert Buntrock (Wed Jan 21 15:02:33 EST 2015)
I did finally locate the original JACS article at a nearby university library. There is no mention of reversing the reaction and re-hydrogenating the dehydrogenated material, a necessary factor for effective hydrogen storage.
Ben (Mon Jan 12 17:55:10 EST 2015)
Is this 5.5 wt. % a material or system target? Last I recall from the Engineering Center of Excellence required at least 7.8 wt% for current system designs to meet system targets.

http://energy.gov/eere/fuelcells/downloads/hydrogen-storage-materials-requirements-meet-2017-board-hydrogen-storage

And that is for liquids. Is anyone developing a fuel cell vehicle that uses solids fuels?
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