The rapid preparation of porous carbon with an improved capacitance

The typical method for preparing the porous carbon used in supercapacitors (SCs) is time-consuming and energy-intensive. We report a fast and efficient route to synthesize and tailor the structure of porous carbon by a Joule heating technique (JHT) using phenolic resin and precursors. During the JHT process, the time and energy needed are both significantly reduced because the precursor is heated to the target temperature at a rate of 1100 K/s, so the porous carbon is formed with the release of small molecules and the etching of the substrate by K 2 CO 3 . JHT has a higher energy efficiency than traditional carbonization methods in a tube furnace and allows for precise control of the pyrolysis process, thus achieving better control of the material's structure and properties. Samples obtained by JHT contain abundant pores and a large specific surface area (1652.7 m 2 /g), which give an excellent specific capacitance of 476.0 F/g and rate capability (75.1% capacitance retention at 64.0 A/g in an aqueous alkaline electrolyte). Furthermore, in electrolytes of 17.0 mol/kg NaClO 4 (water-in-salt) and 1.0 mol/L TEABF 4 /AN, the symmetric SCs have a maximum energy density of 33.3 and 50.8 Wh/kg at power densities of 220.4 and 376.4 W/kg, respectively. The cells also have good long-term stability, with a nearly 100% Coulombic efficiency, and a capacitance retention of 93.1% in a water-in-salt electrolyte after 10000 cycles, and 88.9% in an organic electrolyte after 8000 cycles. This study shows that JHT has the potential to serve as an ultra-fast method to prepare porous carbons for energy storage.