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

摘要

The molten salts can be used as media for hydrocarbon pyrolysis owing totheir excellent thermal properties, fluidity, and ease of products separation.The bubbling of hydrocarbon gases through the molten salts is an effectiveapproach for exploiting the comprehensive advantages of the molten salts.However, the catalytic capability of the molten salts to crack CH bonds islower than that of molten metals/alloys. Although the addition of transitionmetal salts into molten salts improves the catalytic performance, the catalyticmechanism is far from well understood. Herein, bubbling chemical vapordeposition (B-CVD) for one-pot synthesis of 0D (carbon black, CB)/2D (graphene,Gr) carbon materials in molten salt at 850 °C is developed. Spectroscopicresults suggest that the ionic complexes of the transition metal (Cr, Fe,Ru, Ni, Pd, Cu) chloride are the active species to realize the efficient pyrolysisof methane (CH_4). The confined space introduced by the bubble acts as amini-reactor to define the product morphology and accelerate the growth.Beneficial to the synergistic effect between ionic complex promotion andbubble confined space, the mass production of CB/Gr simultaneously withhigh efficiency and low cost at relatively low temperature is achieved.