New molecule brings hydrogen storage closer

Australian and Taiwanese scientists have discovered a new molecule that is bringing the science community closer to overcoming one of the barriers to using hydrogen fuel cells as a viable power source for cars.

The newly discovered ‘28copper15hydride’ was synthesised by a team led by Professor Chenwei Liu from the National Dong Hwa University in Taiwan, who developed a partial structure model. The chemical structure determination was completed at the Australian Nuclear Science and Technology Organisation (ANSTO) using the crystallography tool ‘KOALA’.

“Anyone with a textbook understanding of chemistry knows the term ‘hydride’ describes a compound which results from when a hydrogen atom with a negative charge is combined with another element in the periodic table,” said Dr Alison Edwards, a chemical crystallographer at ANSTO’s Bragg Institute.

“This study revealed that mixing certain copper (Cu) compounds with a hydride of boron (borohydride or (BH₄)) created our newly discovered ‘Chinese Puzzle molecule’, with a new structure that has alternating layers of hydride and copper wrapped in an outer shell of protecting molecules.”

The KOALA is a neutron beam instrument that allows scientists to see the precise location of hydrogen in structures, which is effectively invisible, with X-rays. According to Dr Edwards, the team found that the molecule “actually contained no less than 15 hydrides in the core - which is almost double the eight we were expecting”.

 “This new molecule has an unprecedented metal hydride core - it is definitely different and much more stable than many previous hydride compounds,” she said. “In fact, it is stable in air, which many others are not. So we see there is probably much more yet to learn about the properties, and potential of, hydride.”

Scientists say the molecule puts us on a road to better understanding hydrogen and potentially even how to get it in and out of a fuel system, stored in a manner which is stable and safe. But this is just one of several problems with using hydrogen as fuel, including:

• efficiency, because the process of obtaining hydrogen costs some of the actual energy content already stored in the source of the hydrogen;
• transportation and a lack of adequate mechanism to store large volumes at high density;
• the fuel cell technology is not yet advanced enough; and,
• the distribution infrastructure has not been established.

While Dr Edwards admits that scientists “don’t know how long the road [towards hydrogen-powered cars] is”, she noted, “The implications from the research are actually broader and have impacts beyond car power sources.

“The same synthetic chemistry is being applied in the areas of gold and silver nanoparticle formation, which are currently believed to have wide-ranging potential applications in fields such as catalysis, medical diagnostics and therapeutics.”

The findings have been published in the journal Angewandte Chemie and were presented by Dr Edwards at the 41st International Conference on Coordination in Singapore.

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