The dark, brittle material is ideally suited for this purpose: “It soaks up the unwanted greenhouse gas like a sponge. Other components of the exhaust gas flow hardly stick to it,” says Ansgar Kretzschmar, doctoral researcher at IEK-9. Once saturated, the carbon fibres can later release the CO₂ in its pure form, either to store the gas or, with the help of renewable electricity, to convert it into valuable chemicals.

The material is thus markedly superior to an established CO₂ trap: activated carbon. While the latter is inexpensive and easy to regenerate, it also soaks up other compounds from the exhaust gas flow, which is detrimental to the separating effect. In order to be able to process the carbon dioxide further, however, it must be obtained in as pure a form as possible.

The novel material from Jülich is also made of carbon, but its secret lies in its inner structure: “It consists of extremely thin carbon fibres, only 200 nanometres in diameter. That is more than a hundred times thinner than a human hair,” explains ­Victor Selmert. The vast number of these nanofibres results in a large total surface area, which allows them to bind high amounts of carbon dioxide. This is made possible by a special manufacturing method: electrospinning.

“A plastic solution is spun under high voltage in an electric field. This gives us a very fine mesh of filigree polymer fibres,” Selmert says. In the absence of oxygen, the polymer is then converted into carbon at temperatures of up to 1,200 degrees Celsius. “This creates slit-shaped, thin pores in the surface,” explains Ansgar Kretzschmar. “The CO2 molecules fit right into them. And that is exactly why our material binds so selectively to carbon dioxide.” These two properties – the large surface area and the precisely fitting pores – make this material a superior CO₂ sponge.

Arndt Reuning

Read a longer article on this here:
go.fzj.de/CO2-separation