This is actually
very promising. It may also prove
possi8ble to induce setting up as a substrate on to a skin with similar
methods. At least this has real promise
to produce a vast supply and that is well worth going after.
If we are really
lucky it may become possible to produce a graphene skin cheap and easy while
retaining appropriate characteristics.
This is very
good news. We may be able to also lay
down a vapor level of amorphous metal to or even an insulator on top of the
exposed surface, dissolve the carrier and then reduce the graphene layer to
best thickness.
A
Solution For Graphene Production
Materials: Electrochemical exfoliation produces high-quality
graphene in a short time
Beaker Bath
Immersing platinum and
graphite electrodes in an inorganic salt solution and running a current through
it (left) causes sheets of graphene to flake off the graphite into the solution
(center). Later, the researchers painted the graphene onto paper (right), which
maintains its electrical properties when bent.
‘Graphene is easy to
acquire, at least in small amounts. The first scientists to isolate the strong,
two-dimensional carbon material simply pressed a piece of Scotch tape to a
chunk of graphite and peeled it off. But mass production of graphene for
commercial uses remains a challenge. Now, scientists have shown they can rapidly produce large
quantities of graphene using a bath of
inorganic salts and an electric current (J.
Am. Chem. Soc. 2014, DOI: 10.1021/ja5017156).
Several other methods
have been developed for producing graphene, but each has its drawbacks. Growing
the carbon sheets takes too long, and chemical vapor deposition requires a
metal catalyst, with a second step to remove the metal. Other methods using
solvents or surfactants can harm the electronic properties of graphene or
produce lower yields.
Xinliang Feng and Klaus Müllen of the Max Planck Institute for Polymer Research, in Mainz, Germany, and their colleagues decided to improve
upon an electrochemical technique for producing graphene. Instead of using
acids, which oxidize the graphene and reduce its conductivity, the
researchers prepared solutions of various salts, including ammonium sulfate,
potassium sulfate, and sodium sulfate. Into their mixtures they placed two
electrodes, one made of platinum and the other of graphite, which is
essentially a conglomeration of many layers of graphene. When they ran 10 V
of direct current through the graphite electrode, it began to shed layers into
the solution, a process called exfoliation. They kept the current running for
three to five minutes, separated the exfoliated flakes from the solution, and
washed away excess salt with water.
The process turned more
than 75% of the graphite electrode into graphene flakes. Approximately 85% of
the flakes consisted of one to three layers of graphene—the most desirable electrical properties come from single and
double layers of graphene.
Of the solutions they
tested, the ammonium sulfate worked the best, producing the highest quality
graphene in the fastest time. In one test, the researchers were able to produce
approximately 16.3 g of graphene in 30 minutes. But Feng sees the potential
to scale up production to the kilogram scale needed for industrial use.
James M. Tour, a synthetic organic
chemist at Rice University, calls the work “very
nice—not the first time such electrochemical exfoliation has been done, but the
authors here get it to work more efficiently.”
The exfoliation process
is also more environmentally friendly than previous methods for generating
graphene, Feng says, and doesn’t require high temperatures. He plans to test
other electrolytes as well as different forms of graphite in an effort to scale
up the process. The individual sheets of graphene, however, are still very
small, at most a few millimeters across. Producing sheets on the centimeter
scale, to build something like a transparent electrode, remains difficult, Feng
says.
To demonstrate a use of
their graphene, the team mixed the powder they produced into N,N’-dimethylformamide to produce a
graphene ink, which they painted in a thin film on a piece of paper. They used
two pieces of treated paper to make a supercapacitor, showing the material’s
potential use in flexible electronics.
Lain-Jong Li, a research fellow
at Academia Sinica, in Taiwan, says his
group has developed a similar process and started a company, Nitronix,
which hopes to produce 100 tons of graphene annually within two years. Feng,
meanwhile, is working with the German chemical company BASF to scale up their
production.
Chemical &
Engineering News
ISSN 0009-2347
Copyright © 2014 American Chemical Society
No comments:
Post a Comment