Scientists promise cheap graphene as carbon capture
Graphene as already been proven to improve the mechanical properties of thermoplastics when blended in small quantities, increasing hardness, scratching resistance or tensile strength. Depending on the weight percentage added, it was shown to not only strengthen cement but make it conductive enough to create large-area heating resistor layers for floor heating. But today’s graphene does not come cheap, which restricts many applications where high volumes would be required.
As reported in Nature, in a paper titled “Gram-scale bottom-up flash graphene synthesis”, the so-called flash graphene is made in 10 milliseconds by heating carbon-containing materials to 3,000 Kelvin. The source material can be nearly anything with carbon content including food waste, plastic waste, petroleum coke, coal, wood clippings or biochar, and the result is what the authors describe as “turbostratic” graphene, exhibiting misaligned layers that are easy to separate, unlike A-B stacked graphene from other processes.
“With the present commercial price of graphene being $67,000 to $200,000 per ton, the prospects for this process look superb,” explains Prof. James Tour, co-author of the paper.
The new process is quick and cheap, only requiring the carbon-based waste to be placed between two electrodes and zapped at 200V with a short electrical pulse. The flash process happens in a custom-designed reactor. While graphene forms, all the non-carbon elements such as oxigen and nitrogen, could also be captured as useful industrial gases.
In their experiments, the researchers have converted mixed plastic waste and rubber tires into graphene, but also used coffee beens.
According to Tour, 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.
“By strengthening concrete with graphene, we could use less concrete for building, and it would cost less to manufacture and less to transport,” Tour explains.
“Essentially, we’re trapping greenhouse gases like carbon dioxide and methane that waste food would have emitted in landfills. 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,” highlighted co-corresponding author Rouzbeh Shahsavari, an adjunct assistant professor of civil and environmental engineering and of materials science and nanoengineering at Rice and president of C-Crete Technologies. “Here, graphene acts both as a 2-D template and a reinforcing agent that controls cement hydration and subsequent strength development.”
In the past, Tour said, “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.” “With our method, that carbon becomes fixed,” he said. “It will not enter the air again.”
used in industrial-scale quantities for material reinforcement.
Credit: Rouzbeh Shahsavari/C-Crete Group
The process aligns with Rice’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.
Tour hopes to produce a kilogram 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,” he said.
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