Characterization of activated biomass carbon from tea leaf for supercapacitor applications

Abstract

In this study, a facile synthesis of chemical and thermal activation of biomass tea-waste materials was explored. A tea-waste biosource carbon was explored by chemical vapor deposition (CVD) method at 700 °C. The KOH-treated carbon (AC-KH) and H₃PO₄-treated carbon (AC-HP) were systematically studied for morphological characteristics and showed good morphological structures and a few transparent focused layered nanosheets. The elemental analysis done by scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed the presence of activated carbon. Fourier transform infrared spectroscopy (FT-IR) showed carbon-containing functional groups. The electrochemical analysis showed cyclic voltammetry (CV) curves for electric double layer capacitance (EDLC) with 3 M KOH electrolyte. The Nyquist plot obtained using electrochemical impedance spectroscopy (EIS) showed charge transfer resistance value (R_ct) of 6.08 Ω. The electrochemical galvanostatic charge-discharge (GCD) study was conducted to obtain the specific capacitance (Scp) values of AC-KH, which were found to be 131.95 F/g at 0.5 A/g and also AC-HP active material was observed 55.76 F/g at 1 A/g. The AC-KH showed superior electrochemical performance when compared to AC-HP material. Hence, AC-KH is a promising active material for high-energy supercapacitor applications.

Keywords: Activated carbon; Biomass; CVD; Supercapacitor; Tea waste.