Tuesday , October 27 2020

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How to Turn Garbage Into Graphene

Carbon may be the building block of life, but it’s also a building block inside a whole bunch of our trash, from the carbon black in tires to banana peels and plastic bags. But for the first time, scientists have found a way to give this underutilized carbon new life.

With a simple jolt of electricity, researchers at Rice University have turned garbage into graphene, a vital material in electronics, solar panels, and even asphalt. The new process, which is called “flash graphene” production, yields bulk quantities of graphene flakes. Not only does this technique produce far more graphene than traditional methods, but it’s also way cheaper and greener, upcycling food waste, plastic, and even coal into a valuable carbon allotrope used in various branches of material science.

“This is a big deal,” James Tour, the Rice University chemist who came up with the process, says in a press statement. “The world throws out 30 percent to 40 percent of all food, because it goes bad, and plastic waste is of worldwide concern. We’ve already proven that any solid carbon-based matter, including mixed plastic waste and rubber tires, can be turned into graphene.”

In a video from Rice, Tour guides viewers through the flash graphene process. First, simple wall outlets power up bays of capacitors at the bottom of a plastic bin. The current produced then travels through electronic components until it reaches two electrodes on the other side. The voltage of the current is high enough that it’s sent through the garbage “with enough energy to break every carbon-carbon bond in the system,” Tour explains. The carbon is heated to about 5,000 degrees Fahrenheit.

When the carbon bonds break, new bonds are constructed to create graphene, which is essentially made up of thin sheets of carbon atoms. In the example shown in the video above, the researchers use carbon black—a material created through the incomplete combustion of petroleum and used as a black pigment in newspaper ink or as a conductive agent in electronics.

The flash graphene process gets its name from the spark of bright light created when the chemical reaction occurs. Most of the energy is not turning into heat, but instead goes into what’s called black-body radiation, a type of thermal electromagnetic radiation. That radiation breaks every carbon-carbon bond and any excess energy leftover is released in the form of the bright flash of light. Flash graphene is made in just 10 milliseconds this way.

Tour says that method is far more efficient than previous methods of producing graphene. In a video from The Science Channel, there’s a complex process outlined that includes using a vacuum to evaporate gold, baking a silicon chip in a plasma etcher, and dissolving gold in a chemical solution. And that’s not even half of the process. Tour says these methods produce only small quantities of graphene.

“Previously, we had taken a copper foil and we could grow graphene on that from many different carbon sources. One of them, for example, being cookies, Girl Scout Cookies, or from dead roaches,” says Tour. “But the problem with that is we could only make about a picogram of graphene, a very, very small amount of graphene that might be suitable for electronics. Here, we can do it in bulk.”

A picogram, mind you, is only one trillionth of a milligram. Now, the Rice team is scaling up to daily production levels in the kilograms.

In the future, Tour says, there are endless uses for his new flash graphene process. It could even save the dying coal industry, he posits. By continuing to mine coal—but using it as a raw material in graphene creation, rather than simply burning it for energy—the industry can stay alive and convert its product into a higher value material.

Graphene sells at about $100 to $200 per gram, while coal averages closer to $100 per ton, according to Tour. And instead of putting out noxious greenhouse gases, miners could turn over coal that can be put into paints, concrete, film, or even asphalt.

“It’s just enormous what we’re going to be able to do with this,” Tour says.

This Article was first published on popularmechanics.com

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