A new method for the synthesis of multi-walled carbon nanotubes makes it possible to use atmospheric carbon dioxide as a raw material. Doshisha University reports.
In recent years, governments of developed countries have decided to reduce their carbon dioxide emissions as it has a greenhouse effect on planet Earth and contributes to climate warming. In this regard, scientists and engineers are trying to replace many traditional technologies with “carbon-free” technologies, in which carbon dioxide is not emitted and ideally absorbed. Since the main component of most plastics and other synthetic materials is carbon, it can be a raw material especially for polymer production.
Takuya Goto and his research team suggested an electrochemical method to convert this gas into multi-walled carbon nanotubes. To do this, the authors used a LiCl-KCl salt solution. The melt was saturated with gaseous CO2 and a semi-immersed nickel substrate was used as the electrode. As a result, an electrochemical reaction of reducing carbon dioxide to solid carbon took place in the contact zone between the electrode and the salt solution. Microscopic analysis has shown that this carbon accumulates in the form of commercially available multi-walled carbon nanotubes.
According to the authors, the process proceeds as follows. In the first step, carbon dioxide is reduced to carbon atoms at the boundary between Ni and LiCl-KCl. In the second step, the electrodeposited carbon atoms form Ni-C compounds on the surface of the nickel electrode. Finally, when the solubility limit of carbon in Ni-C compounds is reached, cylindrical carbon nanotubes grow.
The resulting material can be used in many industries, including the production of carbon-containing composites (CFRP).
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