The dream of using hydrogen gas as a clean fuel, on a large scale, just got a little bit closer. Chemists have developed a new molecule that can drive chemical reactions to store and release hydrogen under mild temperatures and pressures.
“It’s a step towards getting a hydrogen economy, towards getting to a place where we can realistically look at ways of using hydrogen,” says Jonathan Hull, a research chemist at Brookhaven National Laboratory in Upton, N.Y. Hull and his colleagues describe the findings online March 18 in Nature Chemistry.
No harmful emissions are released when hydrogen is burned; only water and energy are produced. But transporting useful quantities of hydrogen gas requires keeping it at very high pressures, a process that takes a lot of energy. For these reasons, scientists are interested in finding safer, easier ways to store hydrogen.
In the new study, Hull’s team created a water-soluble molecule that contains atoms of the metal iridium. That new molecule triggers hydrogen to be converted to a form that remains stored in liquid, even at low pressure. Adding a base such as baking soda to water along with this molecule, which acts as a catalyst, turns the storage process on. The scientists think that the molecule’s special chemical limbs, called hydroxyl groups, help break apart the bonds between two hydrogen atoms so hydrogen can be stored as a liquid.
What’s more, the catalyst can also drive the opposite process. Adding an acid to the solution released hydrogen gas from its storage liquid.
By measuring the amounts of starting ingredients and end results for these reactions, the team found that this molecular switch efficiently packed and unpacked hydrogen. Also, the catch and release processes could be carried out at lower temperatures and pressures than other, previously developed chemical switches that trigger these reactions.
The work “is an advance that will direct research in the future,” says Amanda Morris, a chemist at Virginia Tech in Blacksburg. She adds that the hydrogen packing and unpacking reactions described in the study could have potentially useful applications in making hydrogen-fueled cars.