Molten salt electro‐preparation of graphitic carbons

Abstract

Graphite has been used in a wide range of applications since the discovery due to its great chemical stability, excellent electrical conductivity, availability, and ease of processing. However, the synthesis of graphite materials still remains energy-intensive as they are usually produced through a high-temperature treatment (>3000 • C). Herein, we introduce a molten salt electrochemical approach utilizing carbon dioxide (CO 2 ) or amorphous carbons as raw precursors for graphite synthesis. With the assistance of molten salts, the processes can be conducted at moderate temperatures (700-850 • C). The mechanisms of the electrochemical conversion of CO 2 and amorphous carbons into graphitic materials are presented. Furthermore, the factors that affect the graphitization degree of the prepared graphitic products, such as molten salt composition, working temperature, cell voltage, additives, and electrodes, are discussed. The energy storage applications of these graphitic carbons in batteries and supercapacitors are also summarized. Moreover, the energy consumption and cost estimation of the processes are reviewed, which provides perspectives on the large-scale synthesis of graphitic carbons using this molten salt electrochemical strategy.

Molten salt technique for the synthesis of carbon-based materials for supercapacitors

“…There have been some comprehensive overviews of the preparation of porous carbon materials by the molten salt method, 46,47,59,60 but there is still a lack of a comprehensive summary of the different functions of molten salts. Clarifying the specific roles of molten salts in the reaction system is of great significance for the synthesis of carbon materials with different morphologies and functions.…”

Nucleation-Controlled Production of Sub-50 nm Carbon Nanotubes through Electrochemical Conversion of Carbon Dioxide in Carbonate Molten Salt

“…Molten salt-based CO 2 conversion can be used to convert CO 2 into valuable chemicals and substances, including CO, hollow carbon spheres, graphene, carbon nanofibers (CNFs), and carbon nanotubes (CNTs) [1,[10][11][12][13][14]. Among these substances, CNTs not only have substantial market value but also are widely used in various industries, for instance, in cement [15,16], construction materials [15], batteries, capacitors, sensors [17], and textiles [15,17].…”

“…Additionally, the addition of oxide materials to the electrolyte has been shown to yield CNTs with high crystallinity at high current densities. In particular, borate can be introduced to increase the conductivity of CNTs [2,13,25,26,28,29,[31][32][33][34][35][36][37][38][39][40].…”

Salt-assisted synthesis of advanced carbon-based materials for energy-related applications

“…Considering the depth of the overall synthesis strategies, the major focus is limited only to the chemical methods, including chemical vapor deposition, 17 the hydrothermal process, 18–20 pyrolysis of organic carbon precursors, 21,22 and salt-assisted synthesis. 23–26 The advantages of chemical methods over hard physical ones are demonstrated by their ease in synthesis, high reproducibility, high yields and fewer defects in carbon morphologies. Of the various chemical synthesis pathways, hydrothermal methods belong to wet-chemical processes, which require the precursors, such as glucose, to have abundant solubility in water.…”