Synthesizing activated carbon from coconut shells and evaluating its electrochemical characteristics for supercapacitors

Abstract

Author(s): Sakthivel Ranganathan, Mohamed Arfayeen Rahim, Aruna Ravikumar, Tabassum Fathima Ghouse, Rizwana Rahim, Abinaya Sakthivel

Activated carbon derived from coconut shells underwent successful synthesis employing three distinct chemical activators: NaOH, H₃ PO₄ , and ZnCl₂ . Harvested from highland regions with freshwater environments, coconut shells were solar thermally dried prior to carbonization at 600^?C for 3 hours, followed by thorough activation. Characterization of the samples encompassed X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), to discern crystal structure, functional groups, surface area, and morphology. XRD analysis revealed the formation of an amorphous phase with carbon graphite as the predominant constituent, while impurities such as hydrogen, oxygen, nitrogen, potassium, sodium, phosphorus, calcium, and magnesium were identified. FTIR spectroscopy indicated no significant discrepancies across the three activating agents, affirming successful activation through the presence of –OH, C=O, and C-O functional groups. These findings collectively endorse the potential applicability of coconut shell-based activated carbon in water purification treatments. The compacted activated carbon underwent cyclic voltammetry testing across varied scan rates ranging from 20 mV/s to 100 mV/s, within a potential window of 0.05 to 0.8. Specific capacitance values were recorded at each scan rate: 602.19 F/g, 299.78 F/g, 378.31 F/g, 374.13 F/g, and 286.92 F/g, respectively. Notably, the highest specific capacitance of 600.89 F/g and an energy density of 45.64 Wh/kg were achieved at a scan rate of 20 mV/s. Comparative analysis with prior research indicated that the synthesized activated carbon electrodes in this study exhibited the highest specific capacitance observed to date.

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