New Process can Help Create Bulk Quantities of Pristine Graphene

The environmental impact of building materials, including concrete, can be significantly reduced by a banana peel when it is converted into graphene. While individuals are at it, they can discard the plastic empties.

Now, an innovative process developed by the Rice University laboratory of chemist James Tour can change large amounts of almost any kind of carbon source into useful graphene flakes.

This is a fast and economical process. According to Tour, the “flash graphene” method can transform a ton of plastic, food waste, or coal into graphene at a fraction of the cost needed for other techniques that produce large amounts of graphene.

This is a big deal. The world throws out 30% to 40% 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.

James Tour, Chemist, Department of Chemistry, Rice University

Flash graphene is produced in just 10 ms by simply heating carbon-containing materials to 3,000 K (approximately 5000 °F). The source material can be almost anything containing carbon. Major candidates are coal, petroleum coke, plastic waste, food waste, biochar, and wood clippings. The study has been described in the Nature journal.

“With the present commercial price of graphene being $67,000 to $200,000 per ton, the prospects for this process look superb,” added Tour.

According to him, even if a 0.1% concentration of flash graphene is added to the cement used for binding concrete, it can significantly reduce the latter’s environmental impact by a third. It has been reported that cement production produces as high as 8% of human-made carbon dioxide (CO₂) per year.

By strengthening concrete with graphene, we could use less concrete for building, and it would cost less to manufacture and less to transport. Essentially, we’re trapping greenhouse gases like carbon dioxide and methane that waste food would have emitted in landfills.

James Tour, Chemist, Department of Chemistry, Rice University

Tour added, “We are converting those carbons into graphene and adding that graphene to concrete, thereby lowering the amount of carbon dioxide generated in concrete manufacture. It’s a win-win environmental scenario using graphene.”

 “Turning trash to treasure is key to the circular economy. Here, graphene acts both as a 2D template and a reinforcing agent that controls cement hydration and subsequent strength development,” stated Rouzbeh Shahsavari, the study’s co-corresponding author and an adjunct assistant professor of civil and environmental engineering and of materials science and nanoengineering at Rice University.

Shahsavari is also the president of C-Crete Technologies.

Earlier, “graphene has been too expensive to use in these applications. The flash process will greatly lessen the price while it helps us better manage waste,” added Tour.

“With our method, that carbon becomes fixed,” he further stated. “It will not enter the air again.”

The flash graphene process aligns quite well with the newly declared Carbon Hub initiative at Rice University. The aim of this initiative is to create a zero-emission future in which hydrocarbons from gas and oil are repurposed to produce solid carbon and hydrogen gas with zero emission of CO₂.

Under the novel process, solid carbon can be converted into graphene for asphalt, concrete, clothing, cars, buildings, and much more, added Tour.

Duy Luong, the lead author of the study and graduate student at Rice University, developed the flash joule heating process in Tour’s laboratory for producing bulk quantities of graphene. This process improves upon methods like chemical vapor deposition on a metal foil and exfoliation from graphite that involve relatively more cost and effort to create only a small amount of graphene.

More interestingly, the flash graphene process creates a “turbostratic” graphene that has misaligned layers. These layers can be easily separated.

“A-B stacked graphene from other processes, like exfoliation of graphite, is very hard to pull apart,” stated Tour. “The layers adhere strongly together. But turbostratic graphene is much easier to work with because the adhesion between layers is much lower. They just come apart in solution or upon blending in composites.”

“That’s important, because now we can get each of these single-atomic layers to interact with a host composite,” he further added.

At the laboratory, it was observed that used coffee grounds transformed into pristine single-layer graphene sheets.

According to the scientists, bulk composites of graphene containing plywood, metals, plastic, concrete, and other kinds of building materials would be a huge market for flash graphene. The scientists are already testing plastic and concrete enhanced by graphene.

The flash graphene process is a custom-made reactor that heats material rapidly and releases all non-carbon elements in the form of gas.

When this process is industrialized, elements like oxygen and nitrogen that exit the flash reactor can all be trapped as small molecules because they have value.

James Tour, Chemist, Department of Chemistry, Rice University

Tour further stated that the flash graphene process does not generate excess amounts of heat and directs virtually all of its energy into the target.

“You can put your finger right on the container a few seconds afterwards,” Tour added. “And keep in mind this is almost three times hotter than the chemical vapor deposition furnaces we formerly used to make graphene, but in the flash process the heat is concentrated in the carbon material and none in a surrounding reactor.

“All the excess energy comes out as light, in a very bright flash, and because there aren’t any solvents, it’s a super clean process,” he further added.

When Luong fired up the original small-scale device to identify new phases of material, starting with a carbon black sample, he did not expect to come across graphene.

“This started when I took a look at a Science paper talking about flash Joule heating to make phase-changing nanoparticles of metals,” Luong stated. However, he quickly came to know that the flash graphene process created high-quality graphene and nothing more.

Ksenia Bets, a researcher at Rice University and the co-author of the study, performed atom-level simulations that revealed that temperature is crucial for the rapid formation of graphene.

“We essentially speed up the slow geological process by which carbon evolves into its ground state, graphite,” Bets stated. “Greatly accelerated by a heat spike, it is also stopped at the right instant, at the graphene stage.”

“It is amazing how state-of-the-art computer simulations, notoriously slow for observing such kinetics, reveal the details of high temperature-modulated atomic movements and transformation,” she added.

Tour is hoping to create a kilogram (2.2 pounds) of flash graphene each day within a couple of years, beginning with a project that was newly financed by the Department of Energy to transform the coal sourced by the United States.

“This could provide an outlet for coal in large scale by converting it inexpensively into a much-higher-value building material,” Tour concluded.

Tour received a grant from the Department of Energy to further improve the flash graphene process, which will be co-financed by Universal Matter Ltd., a start-up firm.

The study’s co-authors include graduate students Wala Ali Algozeeb, Weiyin Chen, Paul Advincula, Emily McHugh, Muqing Ren, and Zhe Wang from Rice University; postdoctoral researcher Michael Stanford; academic visitors Rodrigo Salvatierra and Vladimir Mancevski; Mahesh Bhatt from C-Crete Technologies, Stafford in Texas; and assistant research professor Hua Guo from Rice University.

The study’s co-corresponding author is Boris Yakobson, the Karl F. Hasselmann Chair of Engineering and a professor of materials science and nanoengineering and of chemistry.

Tour is also the T.T. and W.F. Chao Chair in Chemistry and a professor of computer science and of materials science and nanoengineering at Rice University.

The study was supported by the National Science Foundation and the Air Force Office of Scientific Research.

Video Credit: Rice University