Preparation of supercapacitor carbon materials from food waste via low-temperature pyrolysis

Abstract

In this study, hydrothermal pyrolysis of food waste (FW) was first performed at temperatures ranging from 160° to 260°C for 1 h to produce carbon materials for use as supercapacitor electrodes for energy storage. The hydrochar (HC) produced at 220 °C and activated by KOH exhibited the best electrochemical performance among the prepared samples. Next, tube-furnace and microwave pyrolysis of the FW was performed at 220 °C for 1 h for comparison. The study explains the effect of different pyrolysis processes on the properties of the prepared carbon materials. The results showed that microwave pyrolysis produced microwave carbon (MC), which exhibited the largest specific surface area (734.4 m2g-1), an optimal pore size, and the best electrochemical properties after KOH activation among the prepared samples. The activated MC exhibited a specific capacitance of 189.7 F g-1 at a current density of 1 A g-1 and 146.0 F g-1 at a high current density of 20 A g-1, corresponding to a capacitance retention rate of 76.96%. The low impedance and ion diffusion resistance of the prepared materials provide a novel avenue for the comprehensive, efficient, simple, and harmless utilization of FW.