Graphene can be made to fold itself into a three-dimensional box, researchers at the University of Maryland have shown.
The world’s thinnest material, graphene is just one atom thick. In response to an electric charge, the researchers triggered minuscule squares of graphene to fold into a box that serves as a hydrogen storage container.
“Just like paper origami that can make complicated 3-D structures from 2-D paper, graphene origami allows us to design and fabricate carbon nanostructures that are not naturally existing but of desirable properties. We have made nano-baskets, as well as these new nano-cages to hold hydrogen and other molecular cargos,”
said mechanical engineer Teng Li.
Hydrogen Storage Density Goals
Hydrogen storage, according to the U.S. Department of Energy, is one of the key enabling technologies for the advancement of hydrogen and fuel cell power technologies, in transportation, stationary, and portable applications.
The DOE is hunting for methods to make storing energy with hydrogen a practical possibility. Their goals include that by 2017, techniques shall be developed that allow storing 5.5 percent hydrogen by weight.
By 2020, the goal would be to stretch this achievement to 7.5 percent.
Li’s team has already gone beyond those goals. The graphene origami boxes have a hydrogen storage density of 9.5 percent hydrogen by weight.
They have also demonstrated the potential to reach an even higher density and doing so is one of their future research goals.
As in other approaches to using graphene in fuel cell technology, such as bimetallic nanoparticles, achieving stability is key.
Hydrogenation-Assisted Graphene Origami
The technique has been named Hydrogenation-Assisted Graphene Origami, or HAGO for short. Essentially, they cut sheets of graphene into a pattern, then atomically attach hydrogen to the carbon atoms of the graphene.
Properly prepared, the grapheme will fold into the box on its own without the electrical trigger.
Applying the electric field can polarize the graphene, causing the folded nanostructure to unfold. When the electric field is shut off, the graphene folds up into a box on its own again.
The DOW’s ultimate goal is to develop onboard automotive hydrogen storage systems that will allow for a driving range of greater than 300 miles, all while meeting packaging, cost, safety, and performance requirements to be competitive with current vehicles.
Reference: Shuze Zhu and Teng Li. Hydrogenation-Assisted Graphene Origami and Its Application in Programmable Molecular Mass Uptake, Storage, and Release ACS Nano, DOI: 10.1021/nn500025t February 24, 2014
