Sustainable Development of Biomass-Derived Activated Carbon Through Chemical and Physical Activations and Its Effect on the Physicochemical and Electrochemical Activity

Activated carbon derived from biomass waste and their application as supercapacitor electrodes have aroused a considerable research interest in recent years. In this work, we demonstrate the use of Coffea canephora leaf (CCL) waste for the preparation of activated carbon as supercapacitor electrodes via chemical activation with straightforward pyrolysis at high temperatures for the first time. Potassium hydroxide with three different concentrations, i.e. 0.1 M, 0.3 M, and 0.5 M, was used as activating agent. The as-prepared activated carbon using 0.3 M KOH (CCL-0.3) displayed good physicochemical properties and exhibited superior electrochemical performance than the other two samples (0.1 and 0.5 M). CCL-0.3 achieved the specific capacitances of 297 F g−1 and 220 F g−1 at 1 A g−1 in 1 M H2SO4 and 1 M Na2SO4 electrolytes, respectively. Moreover, CCL-0.3 in 1 M H2SO4 exhibits the equivalent series resistance (Rs) and the charge transfer resistance (Rct) value of CCL-0.3 in 1 M H2SO4 of 0.73 Ω and 4.9 Ω, respectively. Additionally, this study provides strategies for preparing activated carbon as supercapacitor electrode materials with superior performance via chemical activation with straightforward pyrolysis for the renewable energy storage devices.