Modulating three-dimensional porous carbon from paper mulberry juice by a hydrothermal process for a supercapacitor with excellent performance

Paper mulberry fruit juice, as a sugar-based biomass waste product, was used to make porous carbon by hydrothermal treatment and KOH activation as supercapacitor electrodes. Under different hydrothermal conditions, we investigated the response of hydrochars and the performance of porous carbon as an electrode material. The results showed that the hydrochar obtained at low temperatures and a short duration retained more abundant oxygen-containing functional groups, and had a better surface morphology of well-dispersed carbon microspheres, which facilitated its activation. The maximum specific surface area of porous carbon (AHCT8C180) obtained in this study was 3543.8 m2 g−1 under hydrothermal conditions of 180 °C for 8 h. The corresponding porous carbon, as the material of the electrode in the supercapacitor, achieved a good specific capacitance of 428 F g−1 at a current density of 0.5 A g−1. The symmetric supercapacitor fabricated using AHCT8C180 achieved an energy density of 9.56 Wh kg−1 at a power density of 125 W kg−1, In summary, hydrothermal conditions can optimize the specific surface area (SBET) and pore structure of carbon biomass materials through modulating the structure of hydrochar and the construction of the precursor, guiding the preparation of porous carbon used as an electrode material with superior capacitance.