Scientists turn carbon dioxide into charcoal at room temperature

Researchers used liquid metals to replenish carbon dioxide (CO2) into solid coal with technology that they believe could revolutionize carbon capture and storage and offer a new way to remove greenhouse gases of the atmosphere.

The international team led by Australian University RMIT has developed a liquid metal electrocatalyst that directly converts gaseous carbon dioxide into carbon-containing solids at room temperature.

The catalyst, which is based on non-toxic gallium alloys, also prevents the formation of coke – where solid carbon sticks to the surface of the catalyst – which was a problem in previous work in this area.

The key to all this is the "room temperature" bit. Other methods of preparing carbon nanomaterials usually require working at temperatures of several degrees Celsius, which makes them energy consumers and are not commercially viable.

Similarly, according to the researchers, the technologies that consist in compressing CO2 into a liquid and then injecting it into the subsoil have economic and environmental disadvantages, in particular possible leaks from the storage sites.

And reducing CO2 to high-value products such as chemical raw materials and fuel does not trap carbon permanently. Fuels, for example, are burned, which releases them again.

Torben Daeneke, a RMIT researcher, says that gas to solid conversion could be a more sustainable approach.

"Although we can not literally go back in time, converting carbon dioxide back into coal and burying it in the ground is like rewinding the clock of emissions," he says. .

Dorna Esrafilzadeh, a colleague of Daeneke at RMIT, developed the electrochemical technique to capture and convert atmospheric CO2 into storable solid carbon.

Together with her colleagues, she designed a liquid metal catalyst with specific surface properties that makes it extremely efficient in driving electricity while chemically activating the surface.

The CO2 is dissolved in a beaker containing an electrolytic liquid and a small amount of liquid metal, which is then charged with an electric current.

CO2 slowly transforms into solid carbon flakes, which naturally separate from the surface of the liquid metal, allowing the continuous production of carbonaceous solids.

Esrafilzadeh says that the carbon produced could also be used as an electrode.

"One of the benefits of the process is that carbon can hold an electrical charge and become a supercapacitor. It could therefore be used as a component in future vehicles, "she says.

"The process also produces a synthetic fuel as a by-product, which could also have industrial applications."

Daeneke points out that there is still work to be done, but considers the first results to be "a crucial first step towards solid carbon storage".

German, Chinese, American and Australian researchers participated in this collaboration. The results are published in the journal Nature Communications.