Chapter 5
Mechanisms Involved in the Electrolytic
Fabrication of Carbon Nanostructures
Abstract The formation of various forms of carbon nanostructures in molten salts,
including spherical carbon nanoparticles, carbon nanotubes, carbon nanoscrolls,
graphene and carbon encapsulated structures has been found to depend on various
processing parameters, including the morphology of the graphite feed material and
electrochemical conditions such as the molten salt temperature, the cathode current
density and the atmosphere of the molten salt electrolysis process. The mechanisms
involved in the formation of these carbon nanostructures can be speculated by the
correlation between the characteristics of the products and the processing parameters. This chapter concerns various possible mechanisms by which the electrolytic
formation of carbon nanostructures in molten salts can be explained.
Keywords Molten salts · Graphite · Carbon nanostructures · Graphene ·
Intercalation · Hydrogen · Lithium · Chemical reaction · Electrochemistry
5.1 Electrochemical Erosion of Graphite Under Nominally
Dry Ar
As mentioned in the previous chapter, the morphological and the structural characteristics of carbon nanomaterials produced in molten salts are dependent on those
of the graphite feed materials used as the cathode (Fig. 4.4). When the molten salt
process shown in Fig. 4.2 is conducted under nominally dry argon using a graphite
material with a microstructure including planar microsized flakes as the dominant
microstructural component, a product comprised of tubular carbon nanostructures
with a fraction of spherical carbon nanoparticles can be fabricated.
In addition to the graphite morphology, the current density applied was also found
to influence the products (Fig. 4.3). Under dry Ar, at low current densities (lower
than 0.6 A cm
−2 ), the “chemical reactions” occurred at the interface of the graphite
cathode and the molten LiCl during the electrolysis of LiCl melt was proposed to be
responsible for the formation carbon nanoparticles. One possible chemical reaction
which might occur on the graphite cathode can be assumed as follows [1]:
2Li + 2C = Li 2 C 2 G
◦
800 ◦ C = −44kJ H
◦
800 ◦ C = −60 kJ
(5.1)
© Springer Nature Singapore Pte Ltd. 2020
A. R. Kamali, Green Production of Carbon Nanomaterials in Molten Salts
and Applications, https://doi.org/10.1007/978-981-15-2373-1_5
61
Mechanisms Involved in the Electrolytic
Fabrication of Carbon Nanostructures
Abstract The formation of various forms of carbon nanostructures in molten salts,
including spherical carbon nanoparticles, carbon nanotubes, carbon nanoscrolls,
graphene and carbon encapsulated structures has been found to depend on various
processing parameters, including the morphology of the graphite feed material and
electrochemical conditions such as the molten salt temperature, the cathode current
density and the atmosphere of the molten salt electrolysis process. The mechanisms
involved in the formation of these carbon nanostructures can be speculated by the
correlation between the characteristics of the products and the processing parameters. This chapter concerns various possible mechanisms by which the electrolytic
formation of carbon nanostructures in molten salts can be explained.
Keywords Molten salts · Graphite · Carbon nanostructures · Graphene ·
Intercalation · Hydrogen · Lithium · Chemical reaction · Electrochemistry
5.1 Electrochemical Erosion of Graphite Under Nominally
Dry Ar
As mentioned in the previous chapter, the morphological and the structural characteristics of carbon nanomaterials produced in molten salts are dependent on those
of the graphite feed materials used as the cathode (Fig. 4.4). When the molten salt
process shown in Fig. 4.2 is conducted under nominally dry argon using a graphite
material with a microstructure including planar microsized flakes as the dominant
microstructural component, a product comprised of tubular carbon nanostructures
with a fraction of spherical carbon nanoparticles can be fabricated.
In addition to the graphite morphology, the current density applied was also found
to influence the products (Fig. 4.3). Under dry Ar, at low current densities (lower
than 0.6 A cm
−2 ), the “chemical reactions” occurred at the interface of the graphite
cathode and the molten LiCl during the electrolysis of LiCl melt was proposed to be
responsible for the formation carbon nanoparticles. One possible chemical reaction
which might occur on the graphite cathode can be assumed as follows [1]:
2Li + 2C = Li 2 C 2 G
◦
800 ◦ C = −44kJ H
◦
800 ◦ C = −60 kJ
(5.1)
© Springer Nature Singapore Pte Ltd. 2020
A. R. Kamali, Green Production of Carbon Nanomaterials in Molten Salts
and Applications, https://doi.org/10.1007/978-981-15-2373-1_5
61