Comparison of porous carbon prepared by conventional and microwave-assisted hydrothermal carbonization and its application in supercapacitors

Using Euryale ferox shells as biomass raw material, porous carbon samples were prepared by conventional hydrothermal carbonization and microwave-assisted hydrothermal carbonization followed by KOH activation. Effects of hydrothermal heating method and reaction time on the formation of porous carbon structure were systematically studied. It is found that compared with conventional hydrothermal carbonization, microwave-assisted hydrothermal carbonization can rapidly promote the hydrolysis of biomass and form hydrochar with certain pore structure. This is conducive to improving the activation efficiency and preparing porous carbon with rich pore structure. At the same time, microwave-assisted hydrothermal carbonization can improve the content of oxygen-containing functional groups of porous carbon in a short time. In a three-electrode system, PC-M10m (405 F g⁻¹) has a higher specific capacitance than PC-H6h (388 F g⁻¹) at a current density of 0.5 A g⁻¹. PC-M10m charges and discharges 20,000 times at 10 A g⁻¹ current density, and the capacitance retention rate is 100%. This work provides useful results for developing suitable hydrothermal carbonization process for efficient conversion of biomass into high-performance supercapacitor electrode materials.