Graphene has become something of a celebrity material in recent years due to its conductive, thermal and optical properties, which could make it useful in a range of sensors and semiconductor devices. The material does not store hydrogen well in its original form, according to a team of scientists studying it at the NIST Center for Neutron Research. But if oxidized graphene sheets are stacked atop one another like the decks of a multilevel parking lot, connected by molecules that both link the layers to one another and maintain space between them, the resulting graphene-oxide framework (GOF) can accumulate hydrogen in greater quantities.
Inspired to create GOFs by the metal-organic frameworks that are also under scrutiny for hydrogen storage, the team is just beginning to uncover the new structures' properties. "No one else has ever made GOFs, to the best of our knowledge," says NIST theorist Taner Yildirim. "What we have found so far, though, indicates GOFs can hold at least a hundred times more hydrogen molecules than ordinary graphene oxide does. The easy synthesis, low cost and non-toxicity of graphene make this material a promising candidate for gas storage applications."
The GOFs can retain 1 percent of their weight in hydrogen at a temperature of 77 degrees Kelvin and ordinary atmospheric pressure—roughly comparable to the 1.2 percent that some well-studied metal-organic frameworks can hold, Yildirim says.
Another of the team's potentially useful discoveries is the unusual relationship that GOFs exhibit between temperature and hydrogen absorption. In most storage materials, the lower the temperature, the more hydrogen uptake normally occurs. However, the team discovered that GOFs behave quite differently. Although a GOF can absorb hydrogen, it does not take in significant amounts at below 50 Kelvin (-223 degrees Celsius). Moreover, it does not release any hydrogen below this "blocking temperature"—suggesting that, with further research, GOFs might be used both to store hydrogen and to release it when it is needed, a fundamental requirement in fuel cell applications.
Some of the GOFs' capabilities are due to the linking molecules themselves. The molecules the team used are all benzene-boronic acids that interact strongly with hydrogen in their own right. But by keeping several angstroms of space between the graphene layers—akin to the way pillars hold up a ceiling—they also increase the available surface area of each layer, giving it more spots for the hydrogen to latch on.
According to the team, GOFs will likely perform even better once the team explores their parameters in more detail. "We are going to try to optimize the performance of the GOFs and explore other linking molecules as well," says Jacob Burress, also of NIST. "We want to explore the unusual temperature dependence of absorption kinetics, as well as whether they might be useful for capturing greenhouse gases such as carbon dioxide and toxins like ammonia."
The research is funded in part by the Department of Energy.
* J. Burress, J. Simmons, J. Ford and T.Yildirim. "Gas adsorption properties of graphene-oxide-frameworks and nanoporous benzene-boronic acid polymers." To be presented at the March meeting of the American Physical Society (APS) in Portland, Ore., March 18, 2010. An abstract is available at http://meetings.aps.org/Meeting/MAR10/Event/122133
Chad Boutin | EurekAlert!
Creation of coherent states in molecules by incoherent electrons
23.10.2017 | Tata Institute of Fundamental Research
Taming 'wild' electrons in graphene
23.10.2017 | Rutgers University
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
23.10.2017 | Event News
17.10.2017 | Event News
10.10.2017 | Event News
23.10.2017 | Physics and Astronomy
23.10.2017 | Earth Sciences
23.10.2017 | Health and Medicine