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

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 (CH 4 ). 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.