Preparation of microwave-assisted expired honey-derived electrodes with excellent performance for supercapacitors

Abstract

Microwave and hydrothermal methods were employed to prepare expired honey-based biochar, respectively, followed by KOH activation, carbonization and Co²⁺ catalysis. The effect of microwave heating and the mechanism of Co²⁺ catalysis were investigated using XRD, Raman, XPS and BET results. The biochar heated using microwave technology has interconnected pores, a higher specific surface area (1404.6 m² g⁻¹), a greater macropore volume (1.081 cm³ g⁻¹), oxygen-rich atoms (9.71 at%), and highly graphitized structural characteristics, compared with that obtained using a hydrothermal method which has a lower specific surface area (451.2 m² g⁻¹) and a lower oxygen atom content (8.71 at%). Due to its dominant structural characteristics, supercapacitors (SCs) based on as-prepared expired honey biochar (CMC) exhibit superior capacitive performance, including ultra-high capacitance (up to 780.3 F g⁻¹ at a current density of 0.2 A g⁻¹) and good cycling stability (over 96.7% capacitance retention at 10.0 A g⁻¹ after 10 000 cycles of constant current charge and discharge) in a three-electrode system containing 2.0 M H₂SO₄ electrolyte solution. The excellent electrochemical properties and efficient synthesis of biomass-derived carbon materials provide an economical and feasible strategy for large-scale production of high-performance electrodes.