Synthesis of activated N/O/S-codoped porous carbon from waste sugarcane bagasse cellulose for high energy density solid-state asymmetric supercapacitors

Abstract

Carbon materials (CMs) derived from waste biomass have unique porous structures, excellent electrical conductivity, and superior chemical stability, making them ideal as energy storage materials. However, biomass-derived carbon materials have yet to achieve high energy density. These CMs could be improved by heteroatom doping. In this study, nitrogen, oxygen, and sulfur co-doped activated porous carbon (NOS-WSBC) was synthesized via carbonization of L-cysteine modified waste sugarcane bagasse cellulose followed by KOH/CO₂ activation of doped carbon. L-cysteine concentration was varied to optimize textural and electrochemical properties of NOS-WSBC. As optimized NOS-WSBC 0.5 possesses a superior specific surface area of 1914.76 m²/g and mesopore volume of 0.1138 cm³/g, together with a bulk density of 1.18 g/cm³ and total heteroatom content of 16.25 atom%. Because of these unique features, the NOS-WSBC 0.5 delivered a high gravimetric specific capacitance of 462.3F/g and a volumetric specific capacitance of 542.8F/cm³ at 0.2 A/g in 6 M KOH. A solid-state asymmetric supercapacitor (ASC) device was assembled with WSBC and NOS-WSBC 0.5 electrodes, using KOH loaded PVA/PEG/SiO₂ membrane electrolyte. The ASC delivered a high energy density of 70.47 Wh kg⁻¹ at a power density of 200 W kg⁻¹ and excellent capacitance retention of 97.7 % after 10,000 cycles.