17 November 2010
A compound first made in 1923 releases hydrogen at a lower temperature than ammonia borane, one of the most studied materials for hydrogen storage.
Efficient hydrogen storage is an important step in developing a hydrogen economy. One way of storing hydrogen is in chemical compounds that reversibly release hydrogen when they are heated. Diammoniate of diborane (DADB, [(NH3)2BH2]+[BH4]-) as a hydrogen-containing species has the potential to be a storage material, but the crystal structure of the compound that would give valuable information about its properties has not been resolved until now.
Using a combination of X-ray and neutron powder diffraction patterns, Mark Bowden and Tom Autrey at the Pacific Northwest National Laboratory, Richland, and the Los Alamos National Laboratory, and coworkers resolved the crystal structure. 'DADB is an interesting compound because it contains a high weight fraction of hydrogen, one of the highest for a stable material at room temperature,' says Bowden.
Diammoniate of diborane contains a high weight fraction of hydrogen, one of the highest for a stable material at room temperature
When Bowden and the team heated DADB, they found that it behaved in a similar way to ammonia borane, but DADB releases hydrogen at 85°C, whereas ammonia borane releases hydrogen at 110°C.
Hydrogen release at this temperature is very interesting since it is in this temperature range that a practical hydrogen storage system must operate, says Stewart Parker of the Rutherford Appleton Laboratory, Didcot, UK, but it is important to have better knowledge of the system's reversibility.