Effect of pyrolysis temperature on carbon materials derived from reed residue waste biomass for use in supercapacitor electrodes

Abstract

Activated carbon (AC) obtained by the pyrolysis of reed residue waste has been investigated for its potential application as a high-performance electrode material in supercapacitors. Four different pyrolysis temperatures (500, 600, 700, and 800 °C) were implemented, and the optimum pyrolysis temperature was determined on the basis of the physicochemical properties and electrochemical measurements of the AC materials. AC obtained at a relatively low pyrolysis temperature of 600 °C (denoted as C/600 °C) presented a Hemistepta lyrata (bunge flower)-like porous nanostructure with a high specific surface area of 2074.72 m² g⁻¹ and a large pore volume of 0.930 cm³ g⁻¹. SEM and Raman spectroscopy have been used to inspect the surface morphology and assess the degree of graphitization of the AC materials. Electrochemical performances have been assessed by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. Sample C/600 °C displayed a relatively large capacitance of 228 F g⁻¹ at a current density of 1 A g⁻¹ in 6 m KOH as the electrolyte, and it retained very good cyclic stability with a capacitance retention of 98.1% after 8000 cycles at a current density of 5.0 A g⁻¹. The results imply that C/600 °C derived from reed residue waste constitutes a promising electrochemical supercapacitor electrode material.