Mechanism for One‐Pot Synthesis of 0D‐2D Carbon Materials in the Bubbles Inside Molten Salts

Abstract

The molten salts can be used as media for hydrocarbon pyrolysis owing to their excellent thermal properties, fluidity, and ease of products separation. The bubbling of hydrocarbon gases through the molten salts is an effective approach for exploiting the comprehensive advantages of the molten salts. However, the catalytic capability of the molten salts to crack CH bonds is lower than that of molten metals/alloys. Although the addition of transition metal salts into molten salts improves the catalytic performance, the catalytic mechanism is far from well understood. Herein, bubbling chemical vapor deposition (B‐CVD) for one‐pot synthesis of 0D (carbon black, CB)/2D (graphene, Gr) carbon materials in molten salt at 850 °C is developed. Spectroscopic results suggest that the ionic complexes of the transition metal (Cr, Fe, Ru, Ni, Pd, Cu) chloride are the active species to realize the efficient pyrolysis of methane (CH4). The confined space introduced by the bubble acts as a mini‐reactor to define the product morphology and accelerate the growth. Beneficial to the synergistic effect between ionic complex promotion and bubble confined space, the mass production of CB/Gr simultaneously with high efficiency and low cost at relatively low temperature is achieved.

Carbon‐Based Radar Absorbing Materials toward Stealth Technologies

“…Carbon black (CB) is an amorphous allotrope of carbon with a low density, high conductivity, and high mechanical strength, and is generally derived from the combustion of petroleum products. [72][73][74][75] In particular, it contains more than 90% pure elemental carbon, and is made up of tiny, mostly spherical carbon atoms fused together in clusters known as aggregates. Due to its favorable properties, CB has been the most commonly applied reinforcing carbon filler in the manufacture of composites since the First World War, and is used in applications such as a reinforcing agent to provide mechanical strength to absorber materials.…”

Recent progress in melt pyrolysis: Fabrication and applications of high‐value carbon materials from abundant sources

“…In comparison with other works involving molten Sn, elevating the temperature from 1000 to 1250°C led to graphene formation, further illustrating the promotion of temperature on ordered growth of carbon materials. In Zhao's study, NaCl/KCl melts doped with transition metal chlorides (Cr, Fe, Ru, Ni, Pd, Cu) were employed, achieving the production of graphene and carbon black mixtures, also emphasizing the enhancement of methane thermal pyrolysis activity and the promotion of graphitic carbon formation by transition metal chlorides 41 . The addition of molten salts influences the morphology of carbon products generated in molten metals.…”

“…In Zhao's study, NaCl/KCl melts doped with transition metal chlorides (Cr, Fe, Ru, Ni, Pd, Cu) were employed, achieving the production of graphene and carbon black mixtures, also emphasizing the enhancement of methane thermal pyrolysis activity and the promotion of graphitic carbon formation by transition metal chlorides. 41 The addition of molten salts influences the morphology of carbon products generated in molten met-als. Rahimi et al added a layer of NaBr or KBr to the surface of molten Ni 0.27 Bi 0.73 , promoting the formation of carbon black aggregates and carbon nanotube morphologies rather than the graphitic carbon shapes observed in pure metal systems, as demonstrated in Figure 6E,F.…”