Researchers transform Garbage into Graphene

The new process promises pristine graphene in bulk using waste food, plastic and other materials

A new process from researchers at Rice University can transform bulk quantities of just about any carbon source into valuable graphene flakes. The process is quick and cheap and the new technique can convert a ton of coal, food waste or plastic into graphene for a fraction of the cost used by other bulk graphene-producing methods.

Flash graphene is made in 10 milliseconds by heating carbon-containing materials to 3,000 Kelvin (about 5,000 degrees Fahrenheit). The source material can be nearly anything with carbon content. Food waste, plastic waste, petroleum coke, coal, wood clippings and biochar are prime candidates.

A concentration of as little as 0.1% of flash graphene in the cement used to bind concrete could lessen its massive environmental impact by a third. Production of cement reportedly emits as much as 8% of human-made carbon dioxide every year.

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.

By strengthening concrete with graphene, less concrete needs to be used for building, and it would cost less to manufacture and less to transport by trapping greenhouse gases like carbon dioxide and methane that waste food would have emitted in landfills. Those carbons are being converted into graphene and added to concrete, thereby lowering the amount of carbon dioxide generated in concrete manufacture.

Turning trash to treasure is key to the circular economy, graphene acts both as a 2D template and a reinforcing agent that controls cement hydration and subsequent strength development.

In the past graphene has been too expensive to use in these applications however, manufacturing graphene using the flash process will greatly lessen the price while it helps improve waste management.

The process aligns with Rice University’s recently announced Carbon Hub initiative to create a zero-emissions future that repurposes hydrocarbons from oil and gas to generate hydrogen gas and solid carbon with zero emission of carbon dioxide. The flash graphene process can convert that solid carbon into graphene for concrete, asphalt, buildings, cars, clothing and more.

Flash Joule heating for bulk graphene, developed in the Tour lab by Rice graduate student and lead author Duy Luong, improves upon techniques like exfoliation from graphite and chemical vapour deposition on a metal foil that require much more effort and cost to produce just a little graphene.

The process produces turbostratic graphene, with misaligned layers that are easy to separate. A-B stacked graphene from other processes, like exfoliation of graphite, is very hard to pull apart. 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.

In a flash, carbon black turns into graphene through a technique developed by Rice University scientists. The scalable process promises to quickly turn carbon from any source into bulk graphene. From left: undergraduate intern Christina Crassas, chemist James Tour and graduate students Paul Advincula and Duy Luong. Photo by Jeff Fitlow

The lab noted that used coffee grounds transformed into pristine single-layer sheets of graphene. Bulk composites of graphene with plastic, metals, plywood, concrete and other building materials would be a major market for flash graphene, according to the researchers, who are already testing graphene-enhanced concrete and plastic.

The flash process happens in a custom-designed reactor that heats material quickly and emits all noncarbon elements as gas. When this process is industrialised, elements like oxygen and nitrogen that exit the flash reactor can all be trapped as small molecules because they have value.

The flash process produces very little excess heat, channelling almost all of its energy into the target. You can put your finger on the container a few seconds afterwards because with the flash process, the heat is concentrated in the carbon material and not 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

The researchers hope to produce a kilogram (2.2 pounds) a day of flash graphene within two years, starting with a project recently funded by the Department of Energy to convert U.S.-sourced coal. This could provide an outlet for coal in large scale by converting it inexpensively into a much-higher-value building material.

A grant from the Department of Energy has been awarded to scale up the flash graphene process which will be co-funded by the start-up company, Universal Matter Ltd.

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