Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Columbia University have developed a way to convert carbon dioxide (CO₂), a potent greenhouse gas, into carbon nanofibers.

The new method, which uses tandem electrochemical and thermochemical reactions, runs at relatively low temperatures and ambient pressure.

Locking carbon away

As the scientists describe in the journal Nature Catalysis, this approach could successfully lock carbon away in a useful solid form to offset or even achieve negative carbon emissions.

Unlike current methods, “you can put the carbon nanofibers into cement to strengthen the cement,” said Jingguang Chen, a professor of chemical engineering at Columbia with a joint appointment at Brookhaven Lab who led the research. “That would lock the carbon away in concrete for at least 50 years, potentially longer. By then, the world should be shifted to primarily renewable energy sources that don’t emit carbon.”

As a bonus, the process also produces hydrogen gas (H₂), a promising alternative fuel that, when used, creates zero emissions.

The tandem two-step 

“We found a process that can occur at about a relatively low 400 degrees Celsius, which is a much more practical, industrially achievable temperature.”

The trick was to break the reaction into stages and to use two different types of catalysts—materials that make it easier for molecules to come together and react.

The scientists started by realizing that carbon monoxide (CO) is a much better starting material than CO₂ for making carbon nanofibers (CNF). Then they backtracked to find the most efficient way to generate CO from CO₂.

For the second step, the scientists turned to a heat-activated thermocatalyst made of an iron-cobalt alloy. It operates at temperatures around 400 degrees Celsius, significantly milder than a direct CO₂-to-CNF conversion would require. They also discovered that adding a bit of extra metallic cobalt greatly enhances the formation of the carbon nanofibers.

Truly carbon-negative

“By coupling electrocatalysis and thermocatalysis, we are using this tandem process to achieve things that cannot be achieved by either process alone,” Chen said.

If these processes are driven by renewable energy, the results would be truly carbon-negative, opening new opportunities for CO₂ mitigation, the researchers say.

Citation: Xie, Z., Huang, E., Garg, S. et al. CO₂ fixation into carbon nanofibres using electrochemical–thermochemical tandem catalysis. Nat Catal (2024). https://doi.org/10.1038/s41929-023-01085

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