Tuesday, March 17, 2015

Perfect Flaws, Carbon is Life

Purposefully introducing flaws into graphene used in fuel cells can improve the cells and make them more efficient, researchers are reporting.

While the honeycomb structure found in pristine atom-thick graphene is beautiful, allowing it to have a number of tiny holes results in a proton-selective membrane paving the way for improved fuel cells, they say...

"We found if you just dial the graphene back a little on perfection, you will get the membrane you want," says Franz J. Geiger, a Northwestern chemistry professor. "Everyone always strives to make really pristine graphene, but our data show if you want to get protons through, you need less perfect graphene."

...Naturally occurring defects in the graphene - tiny pinholes where a single carbon atom is absent - triggers a chemical conveyor belt that shuttles protons from the water on one side of the membrane to the other in a few seconds, they found.

In conventional membranes, which can be hundreds of nanometers thick, the desired proton selection takes minutes, compared to the quick transfer in a one-atom-thick layer of graphene, they say.

"...Imagine an electric car that charges in the same time it takes to fill a car with gas," says Geiger.

In simple terms, graphene, is a thin layer of pure carbon; it is a single, tightly packed layer of carbon atoms that are bonded together in a hexagonal honeycomb lattice...

It is the thinnest compound known to man at one atom thick,
the lightest material known (with 1 square meter coming in at around 0.77 milligrams),
the strongest compound discovered (between 100-300 times stronger than steel and with a tensile stiffness of 150,000,000 psi),
the best conductor of heat at room temperature (at (4.84±0.44) × 10^3 to (5.30±0.48) × 10^3 W·m−1·K−1) and also
the best conductor of electricity known (studies have shown electron mobility at values of more than 15,000 cm2·V−1·s−1).

...it was previously impossible to grow graphene layers on a large scale using crystalline epitaxy on anything other than a metallic substrate. This severely limited its use in electronics as it was difficult, at that time, to separate graphene layers from its metallic substrate without damaging the graphene.

However, studies in 2012 found that by analysing graphene’s interfacial adhesive energy, it is possible to effectually separate graphene from the metallic board on which it is grown, whilst also being able to reuse the board for future applications theoretically an infinite number of times, therefore reducing the toxic waste previously created by this process. Furthermore, the quality of the graphene that was separated by using this method was sufficiently high enough to create molecular electronic devices successfully.

While this research is very highly regarded, the quality of the graphene produced will still be the limiting factor in technological applications...

Being able to create supercapacitors out of graphene will possibly be the largest step in electronic engineering in a very long time.

Emphasis and light formatting mine.

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