Electrochemical properties of porous carbon prepared from dense medium component of coal by using alumina as template.

The dense medium component (DMC) is a coal group with low ash content and fluidity at 200–600 °C, which is separated from coal by the extraction and back-extraction method. According to the principle of flow-encapsulation, using DMC as raw materials is expected to prepare porous carbons with better properties by the template method. In the study, the nano-alumina was used as the templating agent to prepare the porous carbon by mixing DMC, nano-alumina and KOH and carbonizing/activating them at a certain temperature for a certain time in one step. The effects of the template ratio, activation ratio and activation temperature on the performance parameters of porous carbon as electrode materials were investigated by the Ivium Vertex electrochemical workstation. Within the experimental range, the porous carbon obtained with the best performance has a specific surface area of 2659 m2/g and a pore volume of 1.542 cm3/g when the mass ratio of dense-mesosome, nano-alumina, and KOH was 1:2:3, and the activation temperature was 750 °C. An electrode based on the porous carbons exhibited a capacitance of 398 F/g at the current density of 0.1 A/g and 250 F/g at 2.0 A/g. It also showed a cycling stability with 73.4 % capacitance retention after 10,000 cycles in a 6 M KOH electrolyte. In addition, the energy density reaches up to 70.9 Wh/kg at the power density of 5431 W/kg for a symmetrical supercapacitor. During the activation process, the DMC will carry potassium hydroxide to coat the nano-alumina particles at 380 °C so that the DMC can be well dispersed, ensuring the gas generated during the pyrolysis process escape evenly. When the temperature rises to 540 °C, the DMC is solidified. Potassium hydroxide plays a significant role in pore formation, which etches carbon atoms to obtain more microporous structures. This work provides new a new methodological perspective for designing advanced carbon-based materials for capacitive energy storage. [Display omitted] • During activation, the DMC will carry potassium hydroxide to coat the alumina nanoparticles at a temperature of 380°C. • The DMC is solidified at 540 °C and potassium hydroxide etches carbon atoms to obtain more microporous structures. • The addition of nano-alumina made the pore distribution more uniform and the number of mesopore increased. [ABSTRACT FROM AUTHOR]