Published on January 27th, 2014 | by Tina Casey1
“Sugar Opera” Inspires New 3-D Graphene For Advanced Energy Storage
The tubes have been humming with news of a new form of 3-D graphene based on sugar bubbles, though “bubbles” hardly does justice to blown sugar, the centuries-old Chinese folk art that inspired the researchers.
Part performance art, sugar blowing was practiced by street vendors well into modern times, resulting in delicate, sometimes elaborate sculptures that resemble blown glass. It is dying out as a traditional street art but who knows, the new 3-D graphene breakthrough might revive some interest in the form.
Meanwhile, the new “sugar bubble” 3-D graphene is being billed as the key to next-generation supercapcitors, so let’s see that that’s all about.
3-D Graphene And Sugar
Strictly speaking, graphene is a two-dimensional material, in the form of a sheet of carbon only one atom thick.
Graphene has limitless applications for next-generation electronics, photovoltaics and energy storage devices but for obvious reasons the two-dimensional form is incredibly difficult to work with, much less integrate into commercially available devices.
That’s where 3-D graphene comes in. We recently noticed a breakthrough at the Berkeley lab in that regard, where researchers detected 3-D forms of Dirac fermions, one of the key features of graphene, in the common material sodium bismuthate.
As for the sugar angle, the new 3-D graphene, a joint effort by research institutions in Japan and China, begins with glucose, but – not to get ahead of ourselves – the process results in bubbles composed of graphite. Not for nothing but what’s really notable is the Japan-China research collaborative at a time when the two countries are thisclose to shooting each other over the Senkaku Islands.
Researchers at Rice University also recently discovered that sheets of graphene can be created by manipulating plain table sugar, so the idea of a “blown sugar” form of graphene made from sugar isn’t too far out there.
Researchers at Virginia Tech have also come up with an improved “sugar battery,” so the use of graphene sugar bubbles in energy storage isn’t too far out there, either.
However, we digress. Let’s take a closer look at that Japan-China research, which includes the World Premier International Center for Materials Nanoarchitectonics, National Institute for Materials Science, and Waseda University in Japan, with Southeast University and City University of Hong Kong joining in from China (if I missed anybody, the complete list of affiliations is online at nature.com).
3-D “Blown Sugar” Graphene For Supercapacitors
For those of you new to the topic, a supercapacitor is a high-density energy storage device that charges and discharges far more quickly than a conventional battery. As a group, supercapacitors also have a much longer charge/discharge lifespan than typical batteries.
The research team set out to tackle the shortcomings of first-generation 3-D graphene, which they characterize as having poor electrical conductivity, a low surface area, inferior strength, and low elasticity.
They also note that interconnected, reproducible 3-D graphene is not yet available so we’ll take their word for it.
Sugar blowing, like glass blowing, is basically just what it says: using air to stretch and form a material from the inside, using human lung power.
The research team deployed a somewhat more sophisticated process to create a network of bubbles which they are calling strutted graphene (SG).
They define strutted graphene as a series of continuous, graphitic membranes that are connected and supported by graphitic struts.
Here is the result (breaks are mine for readability):
The bubble network consists of mono- or few-layered graphitic membranes that are tightly glued, rigidly fixed and spatially scaffolded by micrometre-scale graphitic struts.
Such a topological configuration provides intimate structural interconnectivities, freeway for electron/phonon transports, huge accessible surface area, as well as robust mechanical properties.
The graphene network thus overcomes the drawbacks of presently available 3D graphene products and opens up a wide horizon for diverse practical usages, for example, high-power high-energy electrochemical capacitors, as highlighted in this work.
The process itself involves a controlled heating of glucose with ammonium chloride (NH4Cl). As the glucose polymerizes (kind of like carmelization, if you’ve ever tried that at home), the gases from the ammonium chloride form it into large bubbles.
The result is a more perfect “sheet to sheet connectivity” compared to current technology, which involves graphene flakes.
Where the rubber really hits the road, though, is the feasibility and cost of scaling up the process into the commercial marketplace.
It looks like the team has this covered, too, with a claim that the ammonium chloride pathway is a high-volume, low cost process that yields a drop-in product.
That sounds much more efficient than the original art of sugar blowing, which as one observer describes it, is like opera but with sugar instead of vocalization, an art form that “challenges the hand, eye, heart, breath, and temperature technique.”
On the other hand, the new 3-D graphene won’t come in the form of miniature animals. Just bubbles.
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