A novel route for creating multi-walled carbon nanotubes enables using atmospheric carbon dioxide as a feedstock. Research from Doshisha University reports.
In recent years, many governments in developed nations have aimed to cut carbon dioxide emissions because of its contribution to the greenhouse effect and climate warming. Scientists and engineers are pursuing carbon-free technologies that minimize or even absorb carbon dioxide, especially in sectors that rely on carbon-based materials. Since polymers and many synthetic materials are rich in carbon, CO2 can be repurposed as a practical raw material for polymer production and related applications.
Researchers led by Takuya Goto proposed an electrochemical method to transform this gas into multi-walled carbon nanotubes. The process employs a molten LiCl-KCl salt medium saturated with gaseous CO2 and a nickel electrode that is partially immersed as the working electrode. In this environment, carbon dioxide undergoes a reduction at the interface between the electrode and the molten salt, depositing carbon in solid form. Microscopic evaluation confirms that the carbon accumulates in the shape of commercially used multi-walled carbon nanotubes.
The researchers describe the reaction sequence as follows. In the initial stage, carbon dioxide is reduced to carbon atoms at the boundary where nickel meets the LiCl-KCl melt. In the next stage, the deposited carbon forms Ni-C compounds on the nickel surface. Finally, once the carbon concentration reaches the solubility limit in the Ni-C phase, cylindrical carbon nanotubes begin to grow from the surface.
The newly formed nanotubes hold promise for a broad range of applications, including the reinforcement of carbon-containing composites such as carbon fiber reinforced polymers (CFRP) and other high-performance materials used across automotive, aerospace, electronics, and consumer products sectors.
This approach aligns with ongoing efforts to reduce reliance on fossil carbon sources. By converting CO2 directly into valuable nanomaterials, it offers the potential for a circular economy where carbon emitted from industrial processes can be repurposed rather than released into the atmosphere.