4.4 Molten Salt Preparation of Metal-Filled Carbon Nanostructures
49
Fig. 4.10 TEM images showing metal (alloy)-filled carbon nanostructures produced in molten
salts. a Filled tin nanotubes produced by the electrolysis of LiCl–0.5% SnCl 2 at 600 °C in Ar, using
a graphite crucible anode and a graphite cathode, reproduced from Ref. [33], copyright 2019, with
permission from Springer Nature; b Pb–Sn alloy encapsulates CNTs produced by the electrolysis
of LiCl containing 0.5% Sn and 0.5% Pb at 600 °C, reproduced from Ref. [32], copyright 2019,
with permission from American Chemical Society
Since the electrodeposited Sn with a melting point of about 232 °C is in a molten
state at the electrolysis temperature of around 800 °C, it can easily sink in the molten
salt to the bottom of the crucible because of its higher density. This phenomenon
can explain the formation of a Sn disk at the bottom of the graphite rod, as can be
observed in Fig. 4.11 [36].
The dilemma recognized in Fig. 4.11 can be solved by the continuous addition
of SnCl 2 into the molten LiCl throughout the electrolysis process. Figure 4.12a
presents the adapted setup which was developed for the large-scale preparation of
Sn-containing carbon nanostructures in molten LiCl. This consists of a graphite rod
immersed in LiCl melt which is used as the cathode during the electrolysis process,
and a graphite crucible which is employed as the anode. In this method, SnCl 2 pellets
are added into the melt through an alumina tube at varying intervals during the electrolysis process. Figure 4.12b presents the potential difference between the graphite
electrodes (anode and cathode) and a Mo pseudo-reference electrode, as can be seen
in Fig. 4.12a. Distinct waves can be observed on the voltage–time curve of Fig. 4.12b,
which is related to the addition of SnCl 2 pellets into the molten salt throughout the
electrolysis. The recorded voltage values contained a 1.2 V potential drop across the
49
Fig. 4.10 TEM images showing metal (alloy)-filled carbon nanostructures produced in molten
salts. a Filled tin nanotubes produced by the electrolysis of LiCl–0.5% SnCl 2 at 600 °C in Ar, using
a graphite crucible anode and a graphite cathode, reproduced from Ref. [33], copyright 2019, with
permission from Springer Nature; b Pb–Sn alloy encapsulates CNTs produced by the electrolysis
of LiCl containing 0.5% Sn and 0.5% Pb at 600 °C, reproduced from Ref. [32], copyright 2019,
with permission from American Chemical Society
Since the electrodeposited Sn with a melting point of about 232 °C is in a molten
state at the electrolysis temperature of around 800 °C, it can easily sink in the molten
salt to the bottom of the crucible because of its higher density. This phenomenon
can explain the formation of a Sn disk at the bottom of the graphite rod, as can be
observed in Fig. 4.11 [36].
The dilemma recognized in Fig. 4.11 can be solved by the continuous addition
of SnCl 2 into the molten LiCl throughout the electrolysis process. Figure 4.12a
presents the adapted setup which was developed for the large-scale preparation of
Sn-containing carbon nanostructures in molten LiCl. This consists of a graphite rod
immersed in LiCl melt which is used as the cathode during the electrolysis process,
and a graphite crucible which is employed as the anode. In this method, SnCl 2 pellets
are added into the melt through an alumina tube at varying intervals during the electrolysis process. Figure 4.12b presents the potential difference between the graphite
electrodes (anode and cathode) and a Mo pseudo-reference electrode, as can be seen
in Fig. 4.12a. Distinct waves can be observed on the voltage–time curve of Fig. 4.12b,
which is related to the addition of SnCl 2 pellets into the molten salt throughout the
electrolysis. The recorded voltage values contained a 1.2 V potential drop across the