New hybrid nanostructures may be right for next-gen green cars: U.S. scientists

A new design for storage materials that uses layers of graphene separated by nanotube pillars of boron nitride, may be a suitable material to store hydrogen fuel in cars, according to U.S. scientists.

The results suggest that the new computational study is "as an excellent candidate for hydrogen storage, providing ample opportunities to further tune this hybrid material for efficient hydrogen storage," said Farzaneh Shayeganfar and Rouzbeh Shahsavari, materials scientists from Rice University in the United States on a study published in the recent issue of the American Chemical Society journal Langmuir.

According to the study, the researchers had already used computer models to determine the resilience and toughness of pillared graphene structures. Then they added boron nitride nanotubes into the mix to model a unique three-dimensional architecture.

The researchers focused the simulations on four variants: pillared structures of boron nitride or pillared boron nitride graphene doped with oxygen or lithium.

The result: at room temperature and in ambient pressure, oxygen-doped boron nitride graphene was proved the best, holding 11.6 percent of its weight in hydrogen of its gravimetric capacity and about 60 grams per liter of its volumetric capacity.

The U.S. Department of Energy has set standards for storage materials that can make hydrogen a practical fuel for light-duty vehicles. It currently aims to develop an economic storage media that can store more than 5.5 percent of its weight and 40 grams per liter in hydrogen under moderate conditions. The ultimate targets are 7.5 weight percent and 70 grams per liter.

"What we're looking for is the sweet spot," Shahsavari said in a statement, describing the ideal conditions as a balance between the material's surface area and weight, as well as the operating temperatures and pressures.

"This is only practical through computational modeling, because we can test a lot of variations very quickly. It would take experimentalists months to do what takes us only days," the scientist said.

The researchers believed that the newly designed structure can easily beat competing technologies like porous boron nitride, metal oxide frameworks and carbon nanotubes and it must be strong enough to easily satisfy the U.S. Department of Energy's requirement that a hydrogen fuel tank be able to withstand 1,500 charge-discharge cycles. Endi