52
4 Cathodic Exfoliation of Graphite in Molten Salt Electrolytes
Fig. 4.13 Electron micrographs of Sn-filled carbon nanostructures produced by 20 min electrolysis
of the LiCl melt, during which SnCl 2 was gradually introduced into the melt under nominally
pure Ar. a A SEM micrograph showing the presence of CNTs and carbon nanoparticles. b STEM
micrograph of a partially filled carbon nanotube, and EELS spectra recorded on the filled and empty
areas of a CNT, confirming the core–shell morphology of the nanostructures, reproduced from Ref.
[36], copyright 2019, with permission from Elsevier
and high electrical conductivity. The overall features of the reactor used for the
preparation of this hierarchical nanostructured carbon material are similar to that
observed in Fig. 4.2a. In a typical experiment, molten LiCl is electrolyzed at around
800 °C under a dry Ar flow at a constant direct current with an initial cathode
current density of 1 A cm
−2 for about 20 min. Then, the dry Ar gas is replaced by
a moist Ar gas flow, and the electrolysis process is continued for another 60 min.
Under this condition, the graphite cathode becomes exfoliated into an interconnected
mesoporous mixture of carbon nanoscrolls and graphene nanosheets. In order to
remove the residual salts, the carbon nanostructures produced are heated to a high
temperature (greater than the evaporation temperature of the incorporated salts under
a protective atmosphere) [13].
The structure of the interconnected nanostructured carbon differs from that of the
as-received graphite, as can be seen in Figs. 4.14a and b. In the graphite raw material,
the major diffraction peak at the 2º value of 26.35° indicates an interlayer spacing
of 3.38 Å, while in the interconnected nanostructured carbon, the (002) diffraction
4 Cathodic Exfoliation of Graphite in Molten Salt Electrolytes
Fig. 4.13 Electron micrographs of Sn-filled carbon nanostructures produced by 20 min electrolysis
of the LiCl melt, during which SnCl 2 was gradually introduced into the melt under nominally
pure Ar. a A SEM micrograph showing the presence of CNTs and carbon nanoparticles. b STEM
micrograph of a partially filled carbon nanotube, and EELS spectra recorded on the filled and empty
areas of a CNT, confirming the core–shell morphology of the nanostructures, reproduced from Ref.
[36], copyright 2019, with permission from Elsevier
and high electrical conductivity. The overall features of the reactor used for the
preparation of this hierarchical nanostructured carbon material are similar to that
observed in Fig. 4.2a. In a typical experiment, molten LiCl is electrolyzed at around
800 °C under a dry Ar flow at a constant direct current with an initial cathode
current density of 1 A cm
−2 for about 20 min. Then, the dry Ar gas is replaced by
a moist Ar gas flow, and the electrolysis process is continued for another 60 min.
Under this condition, the graphite cathode becomes exfoliated into an interconnected
mesoporous mixture of carbon nanoscrolls and graphene nanosheets. In order to
remove the residual salts, the carbon nanostructures produced are heated to a high
temperature (greater than the evaporation temperature of the incorporated salts under
a protective atmosphere) [13].
The structure of the interconnected nanostructured carbon differs from that of the
as-received graphite, as can be seen in Figs. 4.14a and b. In the graphite raw material,
the major diffraction peak at the 2º value of 26.35° indicates an interlayer spacing
of 3.38 Å, while in the interconnected nanostructured carbon, the (002) diffraction