Nanoscale graphene origami cages set world record for densest hydrogen storage

University of Maryland research already exceeds DOE hydrogen storage goal for 2020
March 14, 2014

Hydrogenation-assisted graphene origami (HAGO) enables the formation of unconventional carbon nanostructures that can uptake, store and release molecular cargos, such as hydrogen (white dots — breakaway view of cage shown) (credit: Shuze Zhu and Teng Li)

University of Maryland researchers have created the world’s highest-density hydrogen storage system, using “graphene origami.” (The stored hydrogen could be used in a fuel cell during peak hours, as system backup, or for portable, transportation, or industrial applications.).

Shuze Zhu and Teng Li, of the Department of Mechanical Engineering found that they can make tiny squares of graphene (the world’s thinnest material, at just one-carbon-atom thick) fold into a box that will open and close itself in response to an electric charge.  Inside the cage (which contains 37 130 carbon atoms), they’ve stored 1468 hydrogen atoms, and have done so more efficiently than was thought possible.

The U.S. Department of Energy is searching for ways to make storing energy with hydrogen a practical possibility, and they set up some goals for onboard automotive hydrogen storage systems with a driving range of 300 miles or more: the Department had hoped that by 2017, a research team could pack in 5.5 percent hydrogen by weight, and that by 2020, it could be stretched to 7.5 percent.

Li’s team has already crossed that threshold, with a hydrogen storage density of 9.5 percent hydrogen by weight.  The team has also demonstrated the potential to reach an even higher density, a future research goal.

“Just like paper origami, which 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 have desirable properties,” said Li, an Associate Professor of Mechanical Engineering, a member of the Maryland NanoCenter and the University of Maryland Energy Research Center (UMERC), and a Keystone professor in the A. James Clark School of Engineering.

Forming a graphene nanocage: (a) Patterned graphene is suitably hydrogenated (by bonding hydrogen atoms to the carbon atoms of planar graphene, thus warping it) and then folded (b-f) into a nanocage via electric-field assistance. (Credit: Shuze Zhu and Teng Li/ACS Nano)

“In this paper, we show that graphene nanocages can be used for hydrogen storage with extraordinary capacity, holding the promise to exceed the year 2020 goal of the U.S. Department of Energy on hydrogen storage,” Li explained to KurzweilAI in an email interview.

“Paper origami has existed for more than a millennium. Such a concept has been explored to enable the formation of complicated 3D structures from 2D building blocks in recent years, such as micro-robots and actuators. In these developments, the building block materials are still bulk materials, with a final resulting 3D structure of size on the order of millimeters.

“The graphene origami we demonstrate in this paper uses the thinnest yet strongest materials ever made (one atom thick), leading to a nanocage on the order of several nanometers. Another unique feature of [Hydrogenation-assisted graphene origami] HAGO that does not exist in conventional origami is that programmable opening and closing of HAGO-enabled nanostructures can be controlled via an external electric field.

“Such a feature is highly desirable and crucial for programmable uptaking, storing and releasing molecular cargos via these HAGO-enabled nanostructures, and further more suggests that it is possible to control a large number of such tiny structures by simply tuning the electric field.”

The U.S. National Science Foundation supported the team’s research, published in the journal ACS Nano.

Abstract of ACS Nano paper

The malleable nature of atomically thin graphene makes it a potential candidate material for nanoscale origami, a promising bottom-up nanomanufacturing approach to fabricating nanobuilding blocks of desirable shapes. The success of graphene origami hinges upon precise and facile control of graphene morphology, which still remains as a significant challenge. Inspired by recent progresses on functionalization and patterning of graphene, we demonstrate hydrogenation-assisted graphene origami (HAGO), a feasible and robust approach to enabling the formation of unconventional carbon nanostructures, through systematic molecular dynamics simulations. A unique and desirable feature of HAGO-enabled nanostructures is the programmable tunability of their morphology via an external electric field. In particular, we demonstrate reversible opening and closing of a HAGO-enabled graphene nanocage, a mechanism that is crucial to achieve molecular mass uptake, storage, and release. HAGO holds promise to enable an array of carbon nanostructures of desirable functionalities by design. As an example, we demonstrate HAGO-enabled high-density hydrogen storage with a weighted percentage exceeding the ultimate goal of US Department of Energy.