Biomass Waste-Derived Rubber Seed Shell Functionalized Porous Carbon As an Inexpensive and Sustainable Energy Material for Supercapacitors

Rubber seed shells (RSS) can be used as a supercapacitor cell electrode due to their high carbon content. Carbon electrodes were derived from biomass through pre-carbonization and ball milling processes, with a 0.5 M KOH activator used for chemical activation. Furthermore, a pyrolysis process with a carbonization stage was used for physical activation of the electrodes by varying the activation temperature, which aims to determine the activation temperature on the quality of the carbon electrode from biomass. Pyrolysis of carbonization was carried out by thermogravimetric analysis for 1 h in an atmosphere of N 2 gas at temperatures of 339°C and 600°C to determine the volatile compounds at the carbon electrode. Physical activation pyrolysis was carried out in a CO 2 gas atmosphere with temperature variations of 650°C, 750°C, and 850°C for sample codes RSS-650, RSS-750, and RSS-850, respectively. The microstructure analysis showed that the carbon electrodes were amorphously characterized by the presence of peaks (001) and (002), where the RSS-750 sample produced the lowest Lc value. The surface morphology of the carbon electrodes shows a cavity-shaped pore dominated by mesopores, with the RSS-750 sample comprising the highest carbon content of 95.61% compared to other samples. The isothermal analysis of N 2 gas shows that the RSS-750 sample has the highest specific surface area of 808,655 m 2 /g with a mesopore distribution. Meanwhile, the analysis of the electrochemical properties of supercapacitor cells using the cyclic voltametry and galvanostatic charge-discharge methods showed that the RSS-750 sample had the highest specific capacitance, of 194.567 F/g and 190.4 F/g, respectively. The analysis of physical and electrochemical properties showed that the RSS-750 sample had better performance than the RSS-650 and RSS-850 samples. Rubber seed shells are the first pure biomass to be singlehandedly used as the main material for making carbon electrodes without template methods, composites or other synthetic materials.