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RESEARCHERS at Stanford University, US, have discovered a high-pressure form of the compound ammonia borane (NH₃BH₃), which contains over 30% hydrogen by weight and could be used to store hydrogen in fuel cells.

The new compound, ammonia borane hydrogen (NH₃BH₃(H₂)), was developed by Yu Lin, a graduate student at Stanford, who led the research, Wendy Mao, assistant professor of geological and environmental sciences at Stanford, and Ho-kwang Mao, senior staff scientist at the Geophysical Laboratory at the Carnegie Institution of Washington.

Ammonia borane already has a high hydrogen content, but by increasing the pressure and crushing the compound, 8-12% of molecular hydrogen could be stored in addition to the chemically bonded hydrogen. This began to happen at 6.2 GPa, around 60,000 times greater than standard pressure at the earth’s surface.

The holy grail of hydrogen storage would be to find a way of storing large amounts of hydrogen at ambient temperatures and pressures. Currently, hydrogen must be stored at high pressures or low temperatures to keep it liquid.

"If the material can be stabilised at or near ambient conditions with a large amount of hydrogen content, then I think it will be very promising," says Lin.

The team now intends to investigate the use of catalysts and other alternative chemical pathways to stabilise the system. 

The research was published in the Proceedings of the National Academy of Sciences doi: 10.1073/pnas.0903511106