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Australia: Scientists at the University of New South Wales develop promising new approach to hydrogen storage.
Scientists at the University of New South Wales (UNSW), Australia, are developing a novel way to store hydrogen that could help turn it into a viable portable fuel source. The research centers on using synthesized nanoparticles of the compound sodium borohydride (NaBH4 for those who love chemistry), which when encased inside nickel shells exhibits surprising and practical storage properties including the ability to reabsorb hydrogen and release it at much lower temperatures than previously observed, making it an attractive proposition for transport applications.
Hydrogen is a clean burning fuel that can be extracted from sources including natural gas, biomass, coal and water. One of the major problems in making it a viable alternative fuel is storage – the atoms are so tiny that they can easily escape from many kinds of containers. Also, hydrogen is more volatile than petrol. It can burn like blazes and can react badly to other substances. As no one wants to have a car that can burst into flames when you switch on the engine, this problem has drawn the attention of scientists around the world. When researchers from the UNSW Materials Energy Research Laboratory synthesized nanoparticles of the sodium borohydride and encased these inside nickel shells, the findings took them by surprise. Borohydrides (including lithium and sodium compounds) are known to be effective storage materials, but it was believed that once the energy was released it could not be reabsorbed. As a result, there has been little focus on sodium borohydride.
The new findings indicate that by controlling the size and architecture of these structures, their properties can be made reversible. In other words, NaBH4 absorbs the hydrogen like a sponge and then releases it, making it useful for application in vehicles. In its bulk form, sodium borohydride requires temperatures above 550°C just to release hydrogen. It’s pretty much the same even on the nano-scale, but this core-shell nanostructure saw energy release happening at just 50°C, and significant release at 350°C.
Dr Kondo-Francois Aguey-Zinsou from the School of Chemical Engineering at UNSW says this is a real breakthrough and his team hopes to have it commercialized in three to five years’ time. “No one has ever tried to synthesize these particles at the nanoscale because they thought it was too difficult, and couldn’t be done," he said. "We’re the first to do so, and demonstrate that energy in the form of hydrogen can be stored with sodium borohydride at practical temperatures and pressures.’’
The findings are published in the Journal ACS Nano.
Press Release:
Nano-structures to realise hydrogen’s energy potential
For the first time, engineers at the University of New South Wales have demonstrated that hydrogen can be released and reabsorbed from a promising storage material, overcoming a major hurdle to its use as an alternative fuel source.
Researchers from the Materials Energy Research Laboratory in nanoscale (MERLin) at UNSW have synthesised nanoparticles of a commonly overlooked chemical compound called sodium borohydride and encased these inside nickel shells.
Their unique "core-shell" nanostructure has demonstrated remarkable hydrogen storage properties, including the release of energy at much lower temperatures than previously observed.
“No one has ever tried to synthesise these particles at the nanoscale because they thought it was too difficult, and couldn’t be done. We’re the first to do so, and demonstrate that energy in the form of hydrogen can be stored with sodium borohydride at practical temperatures and pressures,” says Dr Kondo-Francois Aguey-Zinsou from the School of Chemical Engineering at UNSW.
Considered a major a fuel of the future, hydrogen could be used to power buildings, portable electronics and vehicles – but this application hinges on practical storage technology.
Lightweight compounds known as borohydrides (including lithium and sodium compounds) are known to be effective storage materials but it was believed that once the energy was released it could not be reabsorbed – a critical limitation. This perceived “irreversibility” means there has been little focus on sodium borohydride.
However, the result, published last week in the journal ACS Nano, demonstrates for the first time that reversibility is indeed possible using a borohydride material by itself and could herald significant advances in the design of novel hydrogen storage materials.
“By controlling the size and architecture of these structures we can tune theirproperties and make them reversible – this means they can release and reabsorb hydrogen,” says Aguey-Zinsou, lead author on the paper. “We now have a way to tap into all these borohydride materials, which are particularly exciting for application on vehicles because of their highhydrogen storage capacity.”
The researchers observed remarkable improvements in the thermodynamic and kinetic properties of their material. This means the chemical reactions needed to absorb and release hydrogen occurred faster than previously studied materials, and at significantly reduced temperatures – making possible application far more practical.
In its bulk form, sodium borohydride requires temperatures above 550 degrees Celsius just to release hydrogen. Even on the nano-scale the improvements were minimal. However, with their core-shell nanostructure, the researchers saw initial energy release happening at just 50 °C, and significant release at 350 °C.
“The new materials that could be generated by this exciting strategy could provide practical solutions to meet many of the energy targets set by the US Department of Energy,” says Aguey-Zinsou. “The key thing here is that we’ve opened the doorway.”
Media contact:
Myles Gough, UNSW Media Office | 02 9385 1933
