Powder power - a simple, efficient route to hydrogen fuel


23 June 2008

Chemists in the US have developed a simple reaction to make ammonia borane - a powder more hydrogen-dense than even liquid hydrogen. Their one-pot synthesis of this promising hydrogen storage material is reported in the first issue of the new Royal Society of Chemistry journal Energy & Environmental Science.

Hydrogen has significant benefits as a fuel of the future: potentially renewable and sustainable, and, as hydrogen fuel cells emit only water, a green alternative to other more polluting fuels.

Storing hydrogen safely is tricky, however - pressurising hydrogen gas is clearly dangerous for everyday use, and it can only be stored as a liquid under cryogenic conditions.

Chemists like Tom Autrey from Pacific Northwest National Laboratory, US, are addressing the problem by designing materials to store hydrogen safely, such that it can be released at will to power a fuel cell.

Ammonia borane (AB) is a stable white powder which releases hydrogen gas upon heating. Its use as a hydrogen storage material has been hampered by difficulties in making the powder in reasonable yield, but the new research further increases its promise.

Autrey and colleagues discovered a "one-pot" method of making AB while studying its decomposition pathways. He said the group was "pleasantly surprised that under relatively simple reaction conditions the ammonia borane was formed in very high yields."

The group is currently looking at scaling up the reaction to an industrial level. Autrey says the next challenge is to "recycle the solvents to provide the most economical route to synthesise this promising hydrogen storage material."

References

David J. Heldebrant, Energy Environ. Sci., 2008, DOI: 10.1039/b808865a

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